diff --git a/UPGRADE.md b/UPGRADE.md
index 40fa97969e8..1b63111865b 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -1,5 +1,14 @@
 # Upgrade to 3.0
 
+## BC BREAK: Changes in the `Doctrine\DBAL\Connection` API
+
+- The following methods have been removed as leaking internal implementation details: `::getHost()`, `::getPort()`, `::getUsername()`, `::getPassword()`.
+- The `::getDatabase()` method can now return null which means that no database is currently selected.
+
+## BC BREAK: Changes in `Doctrine\DBAL\Driver\SQLSrv\LastInsertId`
+
+- The class stores the last inserted ID as a nullable string, not an integer, which is reflected in the method signatures.
+
 ## BC BREAK: Changes in the `Doctrine\DBAL\Schema` API
 
 - Method `Doctrine\DBAL\Schema\AbstractSchemaManager::_getPortableViewDefinition()` no longer optionally returns false. It will always return a `Doctrine\DBAL\Schema\View` instance.
diff --git a/lib/Doctrine/DBAL/Connection.php b/lib/Doctrine/DBAL/Connection.php
index 83d8a7d5223..d5d94a83f96 100644
--- a/lib/Doctrine/DBAL/Connection.php
+++ b/lib/Doctrine/DBAL/Connection.php
@@ -114,7 +114,7 @@ class Connection implements DriverConnection
     /**
      * The parameters used during creation of the Connection instance.
      *
-     * @var mixed[]
+     * @var array<string, mixed>
      */
     private $params = [];
 
@@ -153,10 +153,10 @@ class Connection implements DriverConnection
     /**
      * Initializes a new instance of the Connection class.
      *
-     * @param mixed[]            $params       The connection parameters.
-     * @param Driver             $driver       The driver to use.
-     * @param Configuration|null $config       The configuration, optional.
-     * @param EventManager|null  $eventManager The event manager, optional.
+     * @param array<string, mixed> $params       The connection parameters.
+     * @param Driver               $driver       The driver to use.
+     * @param Configuration|null   $config       The configuration, optional.
+     * @param EventManager|null    $eventManager The event manager, optional.
      *
      * @throws DBALException
      */
@@ -197,89 +197,41 @@ public function __construct(
     /**
      * Gets the parameters used during instantiation.
      *
-     * @return mixed[]
+     * @return array<string, mixed>
      */
-    public function getParams()
+    public function getParams() : array
     {
         return $this->params;
     }
 
     /**
      * Gets the name of the database this Connection is connected to.
-     *
-     * @return string
      */
-    public function getDatabase()
+    public function getDatabase() : ?string
     {
         return $this->_driver->getDatabase($this);
     }
 
-    /**
-     * Gets the hostname of the currently connected database.
-     *
-     * @return string|null
-     */
-    public function getHost()
-    {
-        return $this->params['host'] ?? null;
-    }
-
-    /**
-     * Gets the port of the currently connected database.
-     *
-     * @return mixed
-     */
-    public function getPort()
-    {
-        return $this->params['port'] ?? null;
-    }
-
-    /**
-     * Gets the username used by this connection.
-     *
-     * @return string|null
-     */
-    public function getUsername()
-    {
-        return $this->params['user'] ?? null;
-    }
-
-    /**
-     * Gets the password used by this connection.
-     *
-     * @return string|null
-     */
-    public function getPassword()
-    {
-        return $this->params['password'] ?? null;
-    }
-
     /**
      * Gets the DBAL driver instance.
-     *
-     * @return Driver
      */
-    public function getDriver()
+    public function getDriver() : Driver
     {
         return $this->_driver;
     }
 
     /**
      * Gets the Configuration used by the Connection.
-     *
-     * @return Configuration
      */
-    public function getConfiguration()
+    public function getConfiguration() : Configuration
     {
         return $this->_config;
     }
 
     /**
      * Gets the EventManager used by the Connection.
-     *
-     * @return EventManager
      */
-    public function getEventManager()
+    public function getEventManager() : EventManager
     {
         return $this->_eventManager;
     }
@@ -287,11 +239,9 @@ public function getEventManager()
     /**
      * Gets the DatabasePlatform for the connection.
      *
-     * @return AbstractPlatform
-     *
      * @throws DBALException
      */
-    public function getDatabasePlatform()
+    public function getDatabasePlatform() : AbstractPlatform
     {
         if ($this->platform === null) {
             $this->detectDatabasePlatform();
@@ -302,10 +252,8 @@ public function getDatabasePlatform()
 
     /**
      * Gets the ExpressionBuilder for the connection.
-     *
-     * @return ExpressionBuilder
      */
-    public function getExpressionBuilder()
+    public function getExpressionBuilder() : ExpressionBuilder
     {
         return $this->_expr;
     }
@@ -347,7 +295,7 @@ public function connect() : void
      *
      * @throws DBALException If an invalid platform was specified for this connection.
      */
-    private function detectDatabasePlatform()
+    private function detectDatabasePlatform() : void
     {
         $version = $this->getDatabasePlatformVersion();
 
@@ -370,11 +318,9 @@ private function detectDatabasePlatform()
      * or the underlying driver connection cannot determine the platform
      * version without having to query it (performance reasons).
      *
-     * @return string|null
-     *
      * @throws Exception
      */
-    private function getDatabasePlatformVersion()
+    private function getDatabasePlatformVersion() : ?string
     {
         // Driver does not support version specific platforms.
         if (! $this->_driver instanceof VersionAwarePlatformDriver) {
@@ -427,10 +373,8 @@ private function getDatabasePlatformVersion()
 
     /**
      * Returns the database server version if the underlying driver supports it.
-     *
-     * @return string|null
      */
-    private function getServerVersion()
+    private function getServerVersion() : ?string
     {
         $connection = $this->getWrappedConnection();
 
@@ -450,9 +394,9 @@ private function getServerVersion()
      *
      * @return bool True if auto-commit mode is currently enabled for this connection, false otherwise.
      */
-    public function isAutoCommit()
+    public function isAutoCommit() : bool
     {
-        return $this->autoCommit === true;
+        return $this->autoCommit;
     }
 
     /**
@@ -465,7 +409,7 @@ public function isAutoCommit()
      * NOTE: If this method is called during a transaction and the auto-commit mode is changed, the transaction is
      * committed. If this method is called and the auto-commit mode is not changed, the call is a no-op.
      *
-     * @see   isAutoCommit
+     * @see isAutoCommit
      *
      * @throws ConnectionException
      * @throws DriverException
@@ -480,7 +424,7 @@ public function setAutoCommit(bool $autoCommit) : void
         $this->autoCommit = $autoCommit;
 
         // Commit all currently active transactions if any when switching auto-commit mode.
-        if ($this->isConnected !== true || $this->transactionNestingLevel === 0) {
+        if (! $this->isConnected || $this->transactionNestingLevel === 0) {
             return;
         }
 
@@ -489,10 +433,8 @@ public function setAutoCommit(bool $autoCommit) : void
 
     /**
      * Sets the fetch mode.
-     *
-     * @param int $fetchMode
      */
-    public function setFetchMode($fetchMode) : void
+    public function setFetchMode(int $fetchMode) : void
     {
         $this->defaultFetchMode = $fetchMode;
     }
@@ -501,58 +443,58 @@ public function setFetchMode($fetchMode) : void
      * Prepares and executes an SQL query and returns the first row of the result
      * as an associative array.
      *
-     * @param string         $statement The SQL query.
-     * @param mixed[]        $params    The query parameters.
-     * @param int[]|string[] $types     The query parameter types.
+     * @param string                                           $query  The SQL query.
+     * @param array<int, mixed>|array<string, mixed>           $params The prepared statement params.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
      *
-     * @return mixed[]|false False is returned if no rows are found.
+     * @return array<string, mixed>|false False is returned if no rows are found.
      *
      * @throws DBALException
      */
-    public function fetchAssoc($statement, array $params = [], array $types = [])
+    public function fetchAssoc(string $query, array $params = [], array $types = [])
     {
-        return $this->executeQuery($statement, $params, $types)->fetch(FetchMode::ASSOCIATIVE);
+        return $this->executeQuery($query, $params, $types)->fetch(FetchMode::ASSOCIATIVE);
     }
 
     /**
      * Prepares and executes an SQL query and returns the first row of the result
      * as a numerically indexed array.
      *
-     * @param string         $statement The SQL query to be executed.
-     * @param mixed[]        $params    The prepared statement params.
-     * @param int[]|string[] $types     The query parameter types.
+     * @param string                                           $query  The SQL query to be executed.
+     * @param array<int, mixed>|array<string, mixed>           $params The prepared statement params.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
+     *
+     * @return array<int, mixed>|false False is returned if no rows are found.
      *
-     * @return mixed[]|false False is returned if no rows are found.
+     * @throws DBALException
      */
-    public function fetchArray($statement, array $params = [], array $types = [])
+    public function fetchArray(string $query, array $params = [], array $types = [])
     {
-        return $this->executeQuery($statement, $params, $types)->fetch(FetchMode::NUMERIC);
+        return $this->executeQuery($query, $params, $types)->fetch(FetchMode::NUMERIC);
     }
 
     /**
      * Prepares and executes an SQL query and returns the value of a single column
      * of the first row of the result.
      *
-     * @param string         $statement The SQL query to be executed.
-     * @param mixed[]        $params    The prepared statement params.
-     * @param int            $column    The 0-indexed column number to retrieve.
-     * @param int[]|string[] $types     The query parameter types.
+     * @param string                                           $query  The SQL query to be executed.
+     * @param array<int, mixed>|array<string, mixed>           $params The prepared statement params.
+     * @param int                                              $column The 0-indexed column number to retrieve.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
      *
      * @return mixed|false False is returned if no rows are found.
      *
      * @throws DBALException
      */
-    public function fetchColumn($statement, array $params = [], $column = 0, array $types = [])
+    public function fetchColumn(string $query, array $params = [], int $column = 0, array $types = [])
     {
-        return $this->executeQuery($statement, $params, $types)->fetchColumn($column);
+        return $this->executeQuery($query, $params, $types)->fetchColumn($column);
     }
 
     /**
      * Whether an actual connection to the database is established.
-     *
-     * @return bool
      */
-    public function isConnected()
+    public function isConnected() : bool
     {
         return $this->isConnected;
     }
@@ -562,7 +504,7 @@ public function isConnected()
      *
      * @return bool TRUE if a transaction is currently active, FALSE otherwise.
      */
-    public function isTransactionActive()
+    public function isTransactionActive() : bool
     {
         return $this->transactionNestingLevel > 0;
     }
@@ -570,10 +512,10 @@ public function isTransactionActive()
     /**
      * Adds identifier condition to the query components
      *
-     * @param mixed[]  $identifier Map of key columns to their values
-     * @param string[] $columns    Column names
-     * @param mixed[]  $values     Column values
-     * @param string[] $conditions Key conditions
+     * @param array<string, mixed> $identifier Map of key columns to their values
+     * @param array<int, string>   $columns    Column names
+     * @param array<int, mixed>    $values     Column values
+     * @param array<int, string>   $conditions Key conditions
      *
      * @throws DBALException
      */
@@ -602,16 +544,16 @@ private function addIdentifierCondition(
      *
      * Table expression and columns are not escaped and are not safe for user-input.
      *
-     * @param string         $tableExpression The expression of the table on which to delete.
-     * @param mixed[]        $identifier      The deletion criteria. An associative array containing column-value pairs.
-     * @param int[]|string[] $types           The types of identifiers.
+     * @param string                                           $table      The SQL expression of the table on which to delete.
+     * @param array<string, mixed>                             $identifier The deletion criteria. An associative array containing column-value pairs.
+     * @param array<int, int|string>|array<string, int|string> $types      The query parameter types.
      *
      * @return int The number of affected rows.
      *
      * @throws DBALException
      * @throws InvalidArgumentException
      */
-    public function delete($tableExpression, array $identifier, array $types = [])
+    public function delete(string $table, array $identifier, array $types = []) : int
     {
         if (empty($identifier)) {
             throw EmptyCriteriaNotAllowed::new();
@@ -622,7 +564,7 @@ public function delete($tableExpression, array $identifier, array $types = [])
         $this->addIdentifierCondition($identifier, $columns, $values, $conditions);
 
         return $this->executeUpdate(
-            'DELETE FROM ' . $tableExpression . ' WHERE ' . implode(' AND ', $conditions),
+            'DELETE FROM ' . $table . ' WHERE ' . implode(' AND ', $conditions),
             $values,
             is_string(key($types)) ? $this->extractTypeValues($columns, $types) : $types
         );
@@ -630,10 +572,8 @@ public function delete($tableExpression, array $identifier, array $types = [])
 
     /**
      * Closes the connection.
-     *
-     * @return void
      */
-    public function close()
+    public function close() : void
     {
         $this->_conn = null;
 
@@ -644,14 +584,12 @@ public function close()
      * Sets the transaction isolation level.
      *
      * @param int $level The level to set.
-     *
-     * @return int
      */
-    public function setTransactionIsolation($level)
+    public function setTransactionIsolation(int $level) : void
     {
         $this->transactionIsolationLevel = $level;
 
-        return $this->executeUpdate($this->getDatabasePlatform()->getSetTransactionIsolationSQL($level));
+        $this->executeUpdate($this->getDatabasePlatform()->getSetTransactionIsolationSQL($level));
     }
 
     /**
@@ -659,7 +597,7 @@ public function setTransactionIsolation($level)
      *
      * @return int The current transaction isolation level.
      */
-    public function getTransactionIsolation()
+    public function getTransactionIsolation() : int
     {
         if ($this->transactionIsolationLevel === null) {
             $this->transactionIsolationLevel = $this->getDatabasePlatform()->getDefaultTransactionIsolationLevel();
@@ -673,16 +611,16 @@ public function getTransactionIsolation()
      *
      * Table expression and columns are not escaped and are not safe for user-input.
      *
-     * @param string         $tableExpression The expression of the table to update quoted or unquoted.
-     * @param mixed[]        $data            An associative array containing column-value pairs.
-     * @param mixed[]        $identifier      The update criteria. An associative array containing column-value pairs.
-     * @param int[]|string[] $types           Types of the merged $data and $identifier arrays in that order.
+     * @param string                                           $table      The SQL expression of the table to update quoted or unquoted.
+     * @param array<string, mixed>                             $data       An associative array containing column-value pairs.
+     * @param array<string, mixed>                             $identifier The update criteria. An associative array containing column-value pairs.
+     * @param array<int, int|string>|array<string, int|string> $types      The query parameter types.
      *
      * @return int The number of affected rows.
      *
      * @throws DBALException
      */
-    public function update($tableExpression, array $data, array $identifier, array $types = [])
+    public function update(string $table, array $data, array $identifier, array $types = []) : int
     {
         $columns = $values = $conditions = $set = [];
 
@@ -698,7 +636,7 @@ public function update($tableExpression, array $data, array $identifier, array $
             $types = $this->extractTypeValues($columns, $types);
         }
 
-        $sql = 'UPDATE ' . $tableExpression . ' SET ' . implode(', ', $set)
+        $sql = 'UPDATE ' . $table . ' SET ' . implode(', ', $set)
                 . ' WHERE ' . implode(' AND ', $conditions);
 
         return $this->executeUpdate($sql, $values, $types);
@@ -709,18 +647,18 @@ public function update($tableExpression, array $data, array $identifier, array $
      *
      * Table expression and columns are not escaped and are not safe for user-input.
      *
-     * @param string         $tableExpression The expression of the table to insert data into, quoted or unquoted.
-     * @param mixed[]        $data            An associative array containing column-value pairs.
-     * @param int[]|string[] $types           Types of the inserted data.
+     * @param string                                           $table The SQL expression of the table to insert data into, quoted or unquoted.
+     * @param array<string, mixed>                             $data  An associative array containing column-value pairs.
+     * @param array<int, int|string>|array<string, int|string> $types The query parameter types.
      *
      * @return int The number of affected rows.
      *
      * @throws DBALException
      */
-    public function insert($tableExpression, array $data, array $types = [])
+    public function insert(string $table, array $data, array $types = []) : int
     {
         if (empty($data)) {
-            return $this->executeUpdate('INSERT INTO ' . $tableExpression . ' () VALUES ()');
+            return $this->executeUpdate('INSERT INTO ' . $table . ' () VALUES ()');
         }
 
         $columns = [];
@@ -734,7 +672,7 @@ public function insert($tableExpression, array $data, array $types = [])
         }
 
         return $this->executeUpdate(
-            'INSERT INTO ' . $tableExpression . ' (' . implode(', ', $columns) . ')' .
+            'INSERT INTO ' . $table . ' (' . implode(', ', $columns) . ')' .
             ' VALUES (' . implode(', ', $set) . ')',
             $values,
             is_string(key($types)) ? $this->extractTypeValues($columns, $types) : $types
@@ -744,16 +682,16 @@ public function insert($tableExpression, array $data, array $types = [])
     /**
      * Extract ordered type list from an ordered column list and type map.
      *
-     * @param int[]|string[] $columnList
-     * @param int[]|string[] $types
+     * @param array<int, string>     $columnList
+     * @param array<int, int|string> $types      The query parameter types.
      *
-     * @return int[]|string[]
+     * @return array<int, int>|array<int, string>
      */
     private function extractTypeValues(array $columnList, array $types)
     {
         $typeValues = [];
 
-        foreach ($columnList as $columnIndex => $columnName) {
+        foreach ($columnList as $columnName) {
             $typeValues[] = $types[$columnName] ?? ParameterType::STRING;
         }
 
@@ -770,13 +708,13 @@ private function extractTypeValues(array $columnList, array $types)
      * you SHOULD use them. In general, they end up causing way more
      * problems than they solve.
      *
-     * @param string $str The name to be quoted.
+     * @param string $identifier The identifier to be quoted.
      *
-     * @return string The quoted name.
+     * @return string The quoted identifier.
      */
-    public function quoteIdentifier($str)
+    public function quoteIdentifier(string $identifier) : string
     {
-        return $this->getDatabasePlatform()->quoteIdentifier($str);
+        return $this->getDatabasePlatform()->quoteIdentifier($identifier);
     }
 
     /**
@@ -790,15 +728,15 @@ public function quote(string $input) : string
     /**
      * Prepares and executes an SQL query and returns the result as an associative array.
      *
-     * @param string         $sql    The SQL query.
-     * @param mixed[]        $params The query parameters.
-     * @param int[]|string[] $types  The query parameter types.
+     * @param string                                           $query  The SQL query.
+     * @param array<int, mixed>|array<string, mixed>           $params The query parameters.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
      *
-     * @return mixed[]
+     * @return array<int, mixed>
      */
-    public function fetchAll($sql, array $params = [], $types = [])
+    public function fetchAll(string $query, array $params = [], array $types = []) : array
     {
-        return $this->executeQuery($sql, $params, $types)->fetchAll();
+        return $this->executeQuery($query, $params, $types)->fetchAll();
     }
 
     /**
@@ -827,10 +765,10 @@ public function prepare(string $sql) : DriverStatement
      * If the query is parametrized, a prepared statement is used.
      * If an SQLLogger is configured, the execution is logged.
      *
-     * @param string                 $query  The SQL query to execute.
-     * @param mixed[]                $params The parameters to bind to the query, if any.
-     * @param int[]|string[]         $types  The types the previous parameters are in.
-     * @param QueryCacheProfile|null $qcp    The query cache profile, optional.
+     * @param string                                           $query  The SQL query to execute.
+     * @param array<int, mixed>|array<string, mixed>           $params The parameters to bind to the query, if any.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
+     * @param QueryCacheProfile|null                           $qcp    The query cache profile, optional.
      *
      * @return ResultStatement The executed statement.
      *
@@ -875,14 +813,14 @@ public function executeQuery(string $query, array $params = [], $types = [], ?Qu
     /**
      * Executes a caching query.
      *
-     * @param string            $query  The SQL query to execute.
-     * @param mixed[]           $params The parameters to bind to the query, if any.
-     * @param int[]|string[]    $types  The types the previous parameters are in.
-     * @param QueryCacheProfile $qcp    The query cache profile.
+     * @param string                                           $query  The SQL query to execute.
+     * @param array<int, mixed>|array<string, mixed>           $params The parameters to bind to the query, if any.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
+     * @param QueryCacheProfile                                $qcp    The query cache profile.
      *
      * @throws CacheException
      */
-    public function executeCacheQuery($query, $params, $types, QueryCacheProfile $qcp) : ResultStatement
+    public function executeCacheQuery(string $query, array $params, array $types, QueryCacheProfile $qcp) : ResultStatement
     {
         $resultCache = $qcp->getResultCacheDriver() ?? $this->_config->getResultCacheImpl();
 
@@ -920,15 +858,15 @@ public function executeCacheQuery($query, $params, $types, QueryCacheProfile $qc
      * Executes an, optionally parametrized, SQL query and returns the result,
      * applying a given projection/transformation function on each row of the result.
      *
-     * @param string  $query    The SQL query to execute.
-     * @param mixed[] $params   The parameters, if any.
-     * @param Closure $function The transformation function that is applied on each row.
-     *                           The function receives a single parameter, an array, that
-     *                           represents a row of the result set.
+     * @param string                                 $query    The SQL query to execute.
+     * @param array<int, mixed>|array<string, mixed> $params   The parameters, if any.
+     * @param Closure                                $function The transformation function that is applied on each row.
+     *                                                          The function receives a single parameter, an array, that
+     *                                                          represents a row of the result set.
      *
-     * @return mixed[] The projected result of the query.
+     * @return array<int, mixed> The projected result of the query.
      */
-    public function project($query, array $params, Closure $function)
+    public function project(string $query, array $params, Closure $function) : array
     {
         $result = [];
         $stmt   = $this->executeQuery($query, $params);
@@ -971,9 +909,9 @@ public function query(string $sql) : ResultStatement
      *
      * This method supports PDO binding types as well as DBAL mapping types.
      *
-     * @param string         $query  The SQL query.
-     * @param mixed[]        $params The query parameters.
-     * @param int[]|string[] $types  The parameter types.
+     * @param string                                           $query  The SQL query.
+     * @param array<int, mixed>|array<string, mixed>           $params The query parameters.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
      *
      * @throws DBALException
      */
@@ -1035,7 +973,7 @@ public function exec(string $statement) : int
      *
      * @return int The nesting level. A value of 0 means there's no active transaction.
      */
-    public function getTransactionNestingLevel()
+    public function getTransactionNestingLevel() : int
     {
         return $this->transactionNestingLevel;
     }
@@ -1048,13 +986,13 @@ public function getTransactionNestingLevel()
      * because the underlying database may not even support the notion of AUTO_INCREMENT/IDENTITY
      * columns or sequences.
      *
-     * @param string|null $seqName Name of the sequence object from which the ID should be returned.
+     * @param string|null $name Name of the sequence object from which the ID should be returned.
      *
      * @return string A string representation of the last inserted ID.
      */
-    public function lastInsertId($seqName = null)
+    public function lastInsertId(?string $name = null) : string
     {
-        return $this->getWrappedConnection()->lastInsertId($seqName);
+        return $this->getWrappedConnection()->lastInsertId($name);
     }
 
     /**
@@ -1088,13 +1026,9 @@ public function transactional(Closure $func)
     /**
      * Sets if nested transactions should use savepoints.
      *
-     * @param bool $nestTransactionsWithSavepoints
-     *
-     * @return void
-     *
      * @throws ConnectionException
      */
-    public function setNestTransactionsWithSavepoints($nestTransactionsWithSavepoints)
+    public function setNestTransactionsWithSavepoints(bool $nestTransactionsWithSavepoints) : void
     {
         if ($this->transactionNestingLevel > 0) {
             throw MayNotAlterNestedTransactionWithSavepointsInTransaction::new();
@@ -1104,15 +1038,13 @@ public function setNestTransactionsWithSavepoints($nestTransactionsWithSavepoint
             throw SavepointsNotSupported::new();
         }
 
-        $this->nestTransactionsWithSavepoints = (bool) $nestTransactionsWithSavepoints;
+        $this->nestTransactionsWithSavepoints = $nestTransactionsWithSavepoints;
     }
 
     /**
      * Gets if nested transactions should use savepoints.
-     *
-     * @return bool
      */
-    public function getNestTransactionsWithSavepoints()
+    public function getNestTransactionsWithSavepoints() : bool
     {
         return $this->nestTransactionsWithSavepoints;
     }
@@ -1262,11 +1194,9 @@ public function rollBack() : void
      *
      * @param string $savepoint The name of the savepoint to create.
      *
-     * @return void
-     *
      * @throws ConnectionException
      */
-    public function createSavepoint($savepoint)
+    public function createSavepoint(string $savepoint) : void
     {
         if (! $this->getDatabasePlatform()->supportsSavepoints()) {
             throw SavepointsNotSupported::new();
@@ -1280,11 +1210,9 @@ public function createSavepoint($savepoint)
      *
      * @param string $savepoint The name of the savepoint to release.
      *
-     * @return void
-     *
      * @throws ConnectionException
      */
-    public function releaseSavepoint($savepoint)
+    public function releaseSavepoint(string $savepoint) : void
     {
         if (! $this->getDatabasePlatform()->supportsSavepoints()) {
             throw SavepointsNotSupported::new();
@@ -1302,11 +1230,9 @@ public function releaseSavepoint($savepoint)
      *
      * @param string $savepoint The name of the savepoint to rollback to.
      *
-     * @return void
-     *
      * @throws ConnectionException
      */
-    public function rollbackSavepoint($savepoint)
+    public function rollbackSavepoint(string $savepoint) : void
     {
         if (! $this->getDatabasePlatform()->supportsSavepoints()) {
             throw SavepointsNotSupported::new();
@@ -1317,10 +1243,8 @@ public function rollbackSavepoint($savepoint)
 
     /**
      * Gets the wrapped driver connection.
-     *
-     * @return DriverConnection
      */
-    public function getWrappedConnection()
+    public function getWrappedConnection() : DriverConnection
     {
         $this->connect();
 
@@ -1330,10 +1254,8 @@ public function getWrappedConnection()
     /**
      * Gets the SchemaManager that can be used to inspect or change the
      * database schema through the connection.
-     *
-     * @return AbstractSchemaManager
      */
-    public function getSchemaManager()
+    public function getSchemaManager() : AbstractSchemaManager
     {
         if ($this->_schemaManager === null) {
             $this->_schemaManager = $this->_driver->getSchemaManager($this);
@@ -1346,11 +1268,9 @@ public function getSchemaManager()
      * Marks the current transaction so that the only possible
      * outcome for the transaction to be rolled back.
      *
-     * @return void
-     *
      * @throws ConnectionException If no transaction is active.
      */
-    public function setRollbackOnly()
+    public function setRollbackOnly() : void
     {
         if ($this->transactionNestingLevel === 0) {
             throw NoActiveTransaction::new();
@@ -1361,11 +1281,9 @@ public function setRollbackOnly()
     /**
      * Checks whether the current transaction is marked for rollback only.
      *
-     * @return bool
-     *
      * @throws ConnectionException If no transaction is active.
      */
-    public function isRollbackOnly()
+    public function isRollbackOnly() : bool
     {
         if ($this->transactionNestingLevel === 0) {
             throw NoActiveTransaction::new();
@@ -1383,7 +1301,7 @@ public function isRollbackOnly()
      *
      * @return mixed The converted value.
      */
-    public function convertToDatabaseValue($value, $type)
+    public function convertToDatabaseValue($value, string $type)
     {
         return Type::getType($type)->convertToDatabaseValue($value, $this->getDatabasePlatform());
     }
@@ -1397,7 +1315,7 @@ public function convertToDatabaseValue($value, $type)
      *
      * @return mixed The converted type.
      */
-    public function convertToPHPValue($value, $type)
+    public function convertToPHPValue($value, string $type)
     {
         return Type::getType($type)->convertToPHPValue($value, $this->getDatabasePlatform());
     }
@@ -1409,9 +1327,9 @@ public function convertToPHPValue($value, $type)
      * @internal Duck-typing used on the $stmt parameter to support driver statements as well as
      *           raw PDOStatement instances.
      *
-     * @param DriverStatement $stmt   The statement to bind the values to.
-     * @param mixed[]         $params The map/list of named/positional parameters.
-     * @param int[]|string[]  $types  The parameter types.
+     * @param DriverStatement                                  $stmt   The statement to bind the values to.
+     * @param array<int, mixed>|array<string, mixed>           $params The map/list of named/positional parameters.
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
      */
     private function _bindTypedValues(DriverStatement $stmt, array $params, array $types) : void
     {
@@ -1451,9 +1369,9 @@ private function _bindTypedValues(DriverStatement $stmt, array $params, array $t
      * @param mixed           $value The value to bind.
      * @param int|string|null $type  The type to bind (PDO or DBAL).
      *
-     * @return mixed[] [0] => the (escaped) value, [1] => the binding type.
+     * @return array<int, mixed> [0] => the (escaped) value, [1] => the binding type.
      */
-    private function getBindingInfo($value, $type)
+    private function getBindingInfo($value, $type) : array
     {
         if (is_string($type)) {
             $type = Type::getType($type);
@@ -1474,12 +1392,12 @@ private function getBindingInfo($value, $type)
      * @internal This is a purely internal method. If you rely on this method, you are advised to
      *           copy/paste the code as this method may change, or be removed without prior notice.
      *
-     * @param mixed[]        $params
-     * @param int[]|string[] $types
+     * @param array<int, mixed>|array<string, mixed>           $params
+     * @param array<int, int|string>|array<string, int|string> $types  The query parameter types.
      *
-     * @return mixed[]
+     * @return array<int, mixed>|array<string, mixed>
      */
-    public function resolveParams(array $params, array $types)
+    public function resolveParams(array $params, array $types) : array
     {
         $resolvedParams = [];
 
@@ -1517,10 +1435,8 @@ public function resolveParams(array $params, array $types)
 
     /**
      * Creates a new instance of a SQL query builder.
-     *
-     * @return QueryBuilder
      */
-    public function createQueryBuilder()
+    public function createQueryBuilder() : QueryBuilder
     {
         return new Query\QueryBuilder($this);
     }
diff --git a/lib/Doctrine/DBAL/Connections/MasterSlaveConnection.php b/lib/Doctrine/DBAL/Connections/MasterSlaveConnection.php
index 9ed48ae6c9c..b1da13c90f7 100644
--- a/lib/Doctrine/DBAL/Connections/MasterSlaveConnection.php
+++ b/lib/Doctrine/DBAL/Connections/MasterSlaveConnection.php
@@ -67,14 +67,15 @@
  *    )
  * ));
  *
- * You can also pass 'driverOptions' and any other documented option to each of this drivers to pass additional information.
+ * You can also pass 'driverOptions' and any other documented option to each of this drivers
+ * to pass additional information.
  */
 class MasterSlaveConnection extends Connection
 {
     /**
      * Master and slave connection (one of the randomly picked slaves).
      *
-     * @var DriverConnection[]|null[]
+     * @var array<string, DriverConnection|null>
      */
     protected $connections = ['master' => null, 'slave' => null];
 
@@ -89,12 +90,16 @@ class MasterSlaveConnection extends Connection
     /**
      * Creates Master Slave Connection.
      *
-     * @param mixed[] $params
+     * @param array<string, mixed> $params
      *
      * @throws InvalidArgumentException
      */
-    public function __construct(array $params, Driver $driver, ?Configuration $config = null, ?EventManager $eventManager = null)
-    {
+    public function __construct(
+        array $params,
+        Driver $driver,
+        ?Configuration $config = null,
+        ?EventManager $eventManager = null
+    ) {
         if (! isset($params['slaves'], $params['master'])) {
             throw new InvalidArgumentException('master or slaves configuration missing');
         }
@@ -114,10 +119,8 @@ public function __construct(array $params, Driver $driver, ?Configuration $confi
 
     /**
      * Checks if the connection is currently towards the master or not.
-     *
-     * @return bool
      */
-    public function isConnectedToMaster()
+    public function isConnectedToMaster() : bool
     {
         return $this->_conn !== null && $this->_conn === $this->connections['master'];
     }
@@ -179,12 +182,8 @@ public function connect($connectionName = null) : void
 
     /**
      * Connects to a specific connection.
-     *
-     * @param string $connectionName
-     *
-     * @return DriverConnection
      */
-    protected function connectTo($connectionName)
+    protected function connectTo(string $connectionName) : DriverConnection
     {
         $params = $this->getParams();
 
@@ -199,12 +198,11 @@ protected function connectTo($connectionName)
     }
 
     /**
-     * @param string  $connectionName
-     * @param mixed[] $params
+     * @param array<string, mixed> $params
      *
-     * @return mixed
+     * @return array<string, mixed>
      */
-    protected function chooseConnectionConfiguration($connectionName, $params)
+    protected function chooseConnectionConfiguration(string $connectionName, array $params) : array
     {
         if ($connectionName === 'master') {
             return $params['master'];
@@ -262,17 +260,17 @@ public function rollBack() : void
     /**
      * {@inheritDoc}
      */
-    public function delete($tableName, array $identifier, array $types = [])
+    public function delete(string $table, array $identifier, array $types = []) : int
     {
         $this->connect('master');
 
-        return parent::delete($tableName, $identifier, $types);
+        return parent::delete($table, $identifier, $types);
     }
 
     /**
      * {@inheritDoc}
      */
-    public function close()
+    public function close() : void
     {
         unset($this->connections['master'], $this->connections['slave']);
 
@@ -285,21 +283,21 @@ public function close()
     /**
      * {@inheritDoc}
      */
-    public function update($tableName, array $data, array $identifier, array $types = [])
+    public function update(string $table, array $data, array $identifier, array $types = []) : int
     {
         $this->connect('master');
 
-        return parent::update($tableName, $data, $identifier, $types);
+        return parent::update($table, $data, $identifier, $types);
     }
 
     /**
      * {@inheritDoc}
      */
-    public function insert($tableName, array $data, array $types = [])
+    public function insert(string $table, array $data, array $types = []) : int
     {
         $this->connect('master');
 
-        return parent::insert($tableName, $data, $types);
+        return parent::insert($table, $data, $types);
     }
 
     /**
@@ -315,7 +313,7 @@ public function exec(string $statement) : int
     /**
      * {@inheritDoc}
      */
-    public function createSavepoint($savepoint)
+    public function createSavepoint(string $savepoint) : void
     {
         $this->connect('master');
 
@@ -325,7 +323,7 @@ public function createSavepoint($savepoint)
     /**
      * {@inheritDoc}
      */
-    public function releaseSavepoint($savepoint)
+    public function releaseSavepoint(string $savepoint) : void
     {
         $this->connect('master');
 
@@ -335,7 +333,7 @@ public function releaseSavepoint($savepoint)
     /**
      * {@inheritDoc}
      */
-    public function rollbackSavepoint($savepoint)
+    public function rollbackSavepoint(string $savepoint) : void
     {
         $this->connect('master');
 
diff --git a/lib/Doctrine/DBAL/Driver.php b/lib/Doctrine/DBAL/Driver.php
index 10ef3488c77..0cfc18cbba1 100644
--- a/lib/Doctrine/DBAL/Driver.php
+++ b/lib/Doctrine/DBAL/Driver.php
@@ -48,7 +48,7 @@ public function getSchemaManager(Connection $conn) : AbstractSchemaManager;
     /**
      * Gets the name of the database connected to for this driver.
      *
-     * @return string The name of the database or NULL if no database is currently selected.
+     * @return string|null The name of the database or NULL if no database is currently selected.
      */
     public function getDatabase(Connection $conn) : ?string;
 }
diff --git a/lib/Doctrine/DBAL/Driver/Connection.php b/lib/Doctrine/DBAL/Driver/Connection.php
index 8ee150ec4f7..89402cfd7f9 100644
--- a/lib/Doctrine/DBAL/Driver/Connection.php
+++ b/lib/Doctrine/DBAL/Driver/Connection.php
@@ -40,12 +40,8 @@ public function exec(string $statement) : int;
 
     /**
      * Returns the ID of the last inserted row or sequence value.
-     *
-     * @param string|null $name
-     *
-     * @return string
      */
-    public function lastInsertId($name = null);
+    public function lastInsertId(?string $name = null) : string;
 
     /**
      * Initiates a transaction.
diff --git a/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php b/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php
index c5a41d335b3..3439e1b96e5 100644
--- a/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php
+++ b/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php
@@ -29,18 +29,14 @@ class DB2Connection implements Connection, ServerInfoAwareConnection
     private $conn = null;
 
     /**
-     * @param mixed[] $params
-     * @param string  $username
-     * @param string  $password
-     * @param mixed[] $driverOptions
+     * @param array<string, mixed> $params
+     * @param array<string, mixed> $driverOptions
      *
      * @throws DB2Exception
      */
-    public function __construct(array $params, $username, $password, $driverOptions = [])
+    public function __construct(array $params, string $username, string $password, array $driverOptions = [])
     {
-        $isPersistent = (isset($params['persistent']) && $params['persistent'] === true);
-
-        if ($isPersistent) {
+        if (isset($params['persistent']) && $params['persistent'] === true) {
             $conn = db2_pconnect($params['dbname'], $username, $password, $driverOptions);
         } else {
             $conn = db2_connect($params['dbname'], $username, $password, $driverOptions);
@@ -56,7 +52,7 @@ public function __construct(array $params, $username, $password, $driverOptions
     /**
      * {@inheritdoc}
      */
-    public function getServerVersion()
+    public function getServerVersion() : string
     {
         /** @var stdClass $serverInfo */
         $serverInfo = db2_server_info($this->conn);
@@ -67,7 +63,7 @@ public function getServerVersion()
     /**
      * {@inheritdoc}
      */
-    public function requiresQueryForServerVersion()
+    public function requiresQueryForServerVersion() : bool
     {
         return false;
     }
@@ -121,7 +117,7 @@ public function exec(string $statement) : int
     /**
      * {@inheritdoc}
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(?string $name = null) : string
     {
         return db2_last_insert_id($this->conn);
     }
diff --git a/lib/Doctrine/DBAL/Driver/Mysqli/MysqliConnection.php b/lib/Doctrine/DBAL/Driver/Mysqli/MysqliConnection.php
index 2c62142a105..6dcd75b5d1f 100644
--- a/lib/Doctrine/DBAL/Driver/Mysqli/MysqliConnection.php
+++ b/lib/Doctrine/DBAL/Driver/Mysqli/MysqliConnection.php
@@ -39,14 +39,12 @@ class MysqliConnection implements Connection, PingableConnection, ServerInfoAwar
     private $conn;
 
     /**
-     * @param mixed[] $params
-     * @param string  $username
-     * @param string  $password
-     * @param mixed[] $driverOptions
+     * @param array<string, mixed> $params
+     * @param array<int, mixed>    $driverOptions
      *
      * @throws MysqliException
      */
-    public function __construct(array $params, $username, $password, array $driverOptions = [])
+    public function __construct(array $params, string $username, string $password, array $driverOptions = [])
     {
         $port = $params['port'] ?? (int) ini_get('mysqli.default_port');
 
@@ -70,7 +68,7 @@ public function __construct(array $params, $username, $password, array $driverOp
         $this->setSecureConnection($params);
         $this->setDriverOptions($driverOptions);
 
-        set_error_handler(static function () {
+        set_error_handler(static function () : void {
         });
         try {
             if (! $this->conn->real_connect($host, $username, $password, $dbname, $port, $socket, $flags)) {
@@ -91,10 +89,8 @@ public function __construct(array $params, $username, $password, array $driverOp
      * Retrieves mysqli native resource handle.
      *
      * Could be used if part of your application is not using DBAL.
-     *
-     * @return mysqli
      */
-    public function getWrappedResourceHandle()
+    public function getWrappedResourceHandle() : mysqli
     {
         return $this->conn;
     }
@@ -107,7 +103,7 @@ public function getWrappedResourceHandle()
      *
      * @link https://jira.mariadb.org/browse/MDEV-4088
      */
-    public function getServerVersion()
+    public function getServerVersion() : string
     {
         $serverInfos = $this->conn->get_server_info();
         if (stripos($serverInfos, 'mariadb') !== false) {
@@ -124,7 +120,7 @@ public function getServerVersion()
     /**
      * {@inheritdoc}
      */
-    public function requiresQueryForServerVersion()
+    public function requiresQueryForServerVersion() : bool
     {
         return false;
     }
@@ -171,9 +167,9 @@ public function exec(string $statement) : int
     /**
      * {@inheritdoc}
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(?string $name = null) : string
     {
-        return $this->conn->insert_id;
+        return (string) $this->conn->insert_id;
     }
 
     /**
@@ -207,12 +203,12 @@ public function rollBack() : void
     /**
      * Apply the driver options to the connection.
      *
-     * @param mixed[] $driverOptions
+     * @param array<int, mixed> $driverOptions
      *
      * @throws MysqliException When one of of the options is not supported.
      * @throws MysqliException When applying doesn't work - e.g. due to incorrect value.
      */
-    private function setDriverOptions(array $driverOptions = [])
+    private function setDriverOptions(array $driverOptions = []) : void
     {
         $supportedDriverOptions = [
             MYSQLI_OPT_CONNECT_TIMEOUT,
@@ -262,11 +258,11 @@ public function ping() : void
     /**
      * Establish a secure connection
      *
-     * @param mixed[] $params
+     * @param array<string, mixed> $params
      *
      * @throws MysqliException
      */
-    private function setSecureConnection(array $params)
+    private function setSecureConnection(array $params) : void
     {
         if (! isset($params['ssl_key']) &&
             ! isset($params['ssl_cert']) &&
diff --git a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php
index d32ecd15317..c2eac6d92a5 100644
--- a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php
+++ b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php
@@ -37,22 +37,15 @@ class OCI8Connection implements Connection, ServerInfoAwareConnection
     /**
      * Creates a Connection to an Oracle Database using oci8 extension.
      *
-     * @param string $username
-     * @param string $password
-     * @param string $db
-     * @param string $charset
-     * @param int    $sessionMode
-     * @param bool   $persistent
-     *
      * @throws OCI8Exception
      */
     public function __construct(
-        $username,
-        $password,
-        $db,
-        $charset = '',
-        $sessionMode = OCI_DEFAULT,
-        $persistent = false
+        string $username,
+        string $password,
+        string $db,
+        string $charset = '',
+        int $sessionMode = OCI_DEFAULT,
+        bool $persistent = false
     ) {
         $dbh = $persistent
             ? @oci_pconnect($username, $password, $db, $charset, $sessionMode)
@@ -71,7 +64,7 @@ public function __construct(
      * @throws UnexpectedValueException If the version string returned by the database server
      *                                  does not contain a parsable version number.
      */
-    public function getServerVersion()
+    public function getServerVersion() : string
     {
         $version = oci_server_version($this->dbh);
 
@@ -95,7 +88,7 @@ public function getServerVersion()
     /**
      * {@inheritdoc}
      */
-    public function requiresQueryForServerVersion()
+    public function requiresQueryForServerVersion() : bool
     {
         return false;
     }
@@ -141,10 +134,10 @@ public function exec(string $statement) : int
     /**
      * {@inheritdoc}
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(?string $name = null) : string
     {
         if ($name === null) {
-            return false;
+            throw new OCI8Exception('The driver does not support identity columns.');
         }
 
         $sql    = 'SELECT ' . $name . '.CURRVAL FROM DUAL';
@@ -155,15 +148,13 @@ public function lastInsertId($name = null)
             throw new OCI8Exception('lastInsertId failed: Query was executed but no result was returned.');
         }
 
-        return (int) $result;
+        return $result;
     }
 
     /**
      * Returns the current execution mode.
-     *
-     * @return int
      */
-    public function getExecuteMode()
+    public function getExecuteMode() : int
     {
         return $this->executeMode;
     }
diff --git a/lib/Doctrine/DBAL/Driver/PDOConnection.php b/lib/Doctrine/DBAL/Driver/PDOConnection.php
index d9b40e923c9..77704b77e81 100644
--- a/lib/Doctrine/DBAL/Driver/PDOConnection.php
+++ b/lib/Doctrine/DBAL/Driver/PDOConnection.php
@@ -18,17 +18,14 @@ class PDOConnection implements Connection, ServerInfoAwareConnection
     private $connection;
 
     /**
-     * @param string       $dsn
-     * @param string|null  $user
-     * @param string|null  $password
-     * @param mixed[]|null $options
+     * @param array<int, mixed> $options
      *
      * @throws PDOException In case of an error.
      */
-    public function __construct($dsn, $user = null, $password = null, ?array $options = null)
+    public function __construct(string $dsn, string $username = '', string $password = '', array $options = [])
     {
         try {
-            $this->connection = new PDO($dsn, (string) $user, (string) $password, (array) $options);
+            $this->connection = new PDO($dsn, $username, $password, $options);
             $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
         } catch (\PDOException $exception) {
             throw new PDOException($exception);
@@ -50,7 +47,7 @@ public function exec(string $statement) : int
     /**
      * {@inheritdoc}
      */
-    public function getServerVersion()
+    public function getServerVersion() : string
     {
         return $this->connection->getAttribute(PDO::ATTR_SERVER_VERSION);
     }
@@ -95,7 +92,7 @@ public function quote(string $input) : string
     /**
      * {@inheritdoc}
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(?string $name = null) : string
     {
         try {
             if ($name === null) {
@@ -111,7 +108,7 @@ public function lastInsertId($name = null)
     /**
      * {@inheritdoc}
      */
-    public function requiresQueryForServerVersion()
+    public function requiresQueryForServerVersion() : bool
     {
         return false;
     }
diff --git a/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Connection.php b/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Connection.php
index 34b7458133d..ae8c43b9d9b 100644
--- a/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Connection.php
+++ b/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Connection.php
@@ -17,7 +17,7 @@ class Connection extends PDOConnection
     /**
      * {@inheritDoc}
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(?string $name = null) : string
     {
         if ($name === null) {
             return parent::lastInsertId($name);
diff --git a/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereConnection.php b/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereConnection.php
index 7b2161a2e68..e815f760bda 100644
--- a/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereConnection.php
+++ b/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereConnection.php
@@ -37,7 +37,7 @@ class SQLAnywhereConnection implements Connection, ServerInfoAwareConnection
      *
      * @throws SQLAnywhereException
      */
-    public function __construct($dsn, $persistent = false)
+    public function __construct(string $dsn, bool $persistent = false)
     {
         $this->connection = $persistent ? @sasql_pconnect($dsn) : @sasql_connect($dsn);
 
@@ -97,7 +97,7 @@ public function exec(string $statement) : int
     /**
      * {@inheritdoc}
      */
-    public function getServerVersion()
+    public function getServerVersion() : string
     {
         $version = $this->query("SELECT PROPERTY('ProductVersion')")->fetchColumn();
 
@@ -109,7 +109,7 @@ public function getServerVersion()
     /**
      * {@inheritdoc}
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(?string $name = null) : string
     {
         if ($name === null) {
             return sasql_insert_id($this->connection);
@@ -148,7 +148,7 @@ public function quote(string $input) : string
     /**
      * {@inheritdoc}
      */
-    public function requiresQueryForServerVersion()
+    public function requiresQueryForServerVersion() : bool
     {
         return true;
     }
diff --git a/lib/Doctrine/DBAL/Driver/SQLSrv/LastInsertId.php b/lib/Doctrine/DBAL/Driver/SQLSrv/LastInsertId.php
index c76e66ff52e..8e688fe34e3 100644
--- a/lib/Doctrine/DBAL/Driver/SQLSrv/LastInsertId.php
+++ b/lib/Doctrine/DBAL/Driver/SQLSrv/LastInsertId.php
@@ -9,21 +9,15 @@
  */
 class LastInsertId
 {
-    /** @var int */
+    /** @var string|null */
     private $id;
 
-    /**
-     * @param int $id
-     */
-    public function setId($id)
+    public function setId(?string $id) : void
     {
         $this->id = $id;
     }
 
-    /**
-     * @return int
-     */
-    public function getId()
+    public function getId() : ?string
     {
         return $this->id;
     }
diff --git a/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php b/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php
index 4470c58cd6d..a6b09b02818 100644
--- a/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php
+++ b/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php
@@ -30,12 +30,11 @@ class SQLSrvConnection implements Connection, ServerInfoAwareConnection
     protected $lastInsertId;
 
     /**
-     * @param string  $serverName
-     * @param mixed[] $connectionOptions
+     * @param array<string, mixed> $connectionOptions
      *
      * @throws SQLSrvException
      */
-    public function __construct($serverName, $connectionOptions)
+    public function __construct(string $serverName, array $connectionOptions)
     {
         if (! sqlsrv_configure('WarningsReturnAsErrors', 0)) {
             throw SQLSrvException::fromSqlSrvErrors();
@@ -54,7 +53,7 @@ public function __construct($serverName, $connectionOptions)
     /**
      * {@inheritdoc}
      */
-    public function getServerVersion()
+    public function getServerVersion() : string
     {
         $serverInfo = sqlsrv_server_info($this->conn);
 
@@ -64,7 +63,7 @@ public function getServerVersion()
     /**
      * {@inheritdoc}
      */
-    public function requiresQueryForServerVersion()
+    public function requiresQueryForServerVersion() : bool
     {
         return false;
     }
@@ -119,7 +118,7 @@ public function exec(string $statement) : int
     /**
      * {@inheritDoc}
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(?string $name = null) : string
     {
         if ($name !== null) {
             $stmt = $this->prepare('SELECT CONVERT(VARCHAR(MAX), current_value) FROM sys.sequences WHERE name = ?');
diff --git a/lib/Doctrine/DBAL/Driver/ServerInfoAwareConnection.php b/lib/Doctrine/DBAL/Driver/ServerInfoAwareConnection.php
index d17b46c3b74..e667dddaf92 100644
--- a/lib/Doctrine/DBAL/Driver/ServerInfoAwareConnection.php
+++ b/lib/Doctrine/DBAL/Driver/ServerInfoAwareConnection.php
@@ -11,15 +11,13 @@ interface ServerInfoAwareConnection
 {
     /**
      * Returns the version number of the database server connected to.
-     *
-     * @return string
      */
-    public function getServerVersion();
+    public function getServerVersion() : string;
 
     /**
      * Checks whether a query is required to retrieve the database server version.
      *
      * @return bool True if a query is required to retrieve the database server version, false otherwise.
      */
-    public function requiresQueryForServerVersion();
+    public function requiresQueryForServerVersion() : bool;
 }
diff --git a/lib/Doctrine/DBAL/Portability/Connection.php b/lib/Doctrine/DBAL/Portability/Connection.php
index 8c64822f9e0..db687b167b4 100644
--- a/lib/Doctrine/DBAL/Portability/Connection.php
+++ b/lib/Doctrine/DBAL/Portability/Connection.php
@@ -82,18 +82,12 @@ public function connect() : void
         }
     }
 
-    /**
-     * @return int
-     */
-    public function getPortability()
+    public function getPortability() : int
     {
         return $this->portability;
     }
 
-    /**
-     * @return int
-     */
-    public function getFetchCase()
+    public function getFetchCase() : ?int
     {
         return $this->case;
     }
diff --git a/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php b/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php
index 64edf7d39d3..0c9e5ea7ffc 100644
--- a/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php
+++ b/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php
@@ -957,7 +957,13 @@ public function createSchemaConfig() : SchemaConfig
      */
     public function getSchemaSearchPaths() : array
     {
-        return [$this->_conn->getDatabase()];
+        $database = $this->_conn->getDatabase();
+
+        if ($database !== null) {
+            return [$database];
+        }
+
+        return [];
     }
 
     /**
diff --git a/lib/Doctrine/DBAL/Schema/DB2SchemaManager.php b/lib/Doctrine/DBAL/Schema/DB2SchemaManager.php
index 7cfbf474530..a0d2312f285 100644
--- a/lib/Doctrine/DBAL/Schema/DB2SchemaManager.php
+++ b/lib/Doctrine/DBAL/Schema/DB2SchemaManager.php
@@ -7,9 +7,7 @@
 use Doctrine\DBAL\Types\Type;
 use const CASE_LOWER;
 use function array_change_key_case;
-use function assert;
 use function is_resource;
-use function is_string;
 use function preg_match;
 use function str_replace;
 use function strpos;
@@ -29,12 +27,9 @@ class DB2SchemaManager extends AbstractSchemaManager
      */
     public function listTableNames() : array
     {
-        $username = $this->_conn->getUsername();
-        assert(is_string($username));
+        $sql = $this->_platform->getListTablesSQL() . ' AND CREATOR = CURRENT_USER';
 
-        $sql = $this->_platform->getListTablesSQL() . ' AND CREATOR = UPPER(?)';
-
-        $tables = $this->_conn->fetchAll($sql, [$username]);
+        $tables = $this->_conn->fetchAll($sql);
 
         return $this->filterAssetNames($this->_getPortableTablesList($tables));
     }
diff --git a/lib/Doctrine/DBAL/Sharding/PoolingShardConnection.php b/lib/Doctrine/DBAL/Sharding/PoolingShardConnection.php
index 72744474cac..aa7823241b0 100644
--- a/lib/Doctrine/DBAL/Sharding/PoolingShardConnection.php
+++ b/lib/Doctrine/DBAL/Sharding/PoolingShardConnection.php
@@ -53,13 +53,13 @@
  */
 class PoolingShardConnection extends Connection
 {
-    /** @var DriverConnection[] */
+    /** @var array<int, DriverConnection>|array<string, DriverConnection> */
     private $activeConnections = [];
 
     /** @var string|int|null */
     private $activeShardId;
 
-    /** @var mixed[] */
+    /** @var array<int, array<string, mixed>>|array<string, array<string, mixed>> */
     private $connectionParameters = [];
 
     /**
@@ -67,8 +67,12 @@ class PoolingShardConnection extends Connection
      *
      * @throws InvalidArgumentException
      */
-    public function __construct(array $params, Driver $driver, ?Configuration $config = null, ?EventManager $eventManager = null)
-    {
+    public function __construct(
+        array $params,
+        Driver $driver,
+        ?Configuration $config = null,
+        ?EventManager $eventManager = null
+    ) {
         if (! isset($params['global'], $params['shards'])) {
             throw new InvalidArgumentException('Connection Parameters require "global" and "shards" configurations.');
         }
@@ -119,51 +123,11 @@ public function getActiveShardId()
     /**
      * {@inheritdoc}
      */
-    public function getParams()
+    public function getParams() : array
     {
         return $this->activeShardId ? $this->connectionParameters[$this->activeShardId] : $this->connectionParameters[0];
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function getHost()
-    {
-        $params = $this->getParams();
-
-        return $params['host'] ?? parent::getHost();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getPort()
-    {
-        $params = $this->getParams();
-
-        return $params['port'] ?? parent::getPort();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getUsername()
-    {
-        $params = $this->getParams();
-
-        return $params['user'] ?? parent::getUsername();
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getPassword()
-    {
-        $params = $this->getParams();
-
-        return $params['password'] ?? parent::getPassword();
-    }
-
     /**
      * Connects to a given shard.
      *
@@ -207,10 +171,8 @@ public function connect($shardId = null) : void
      * Connects to a specific connection.
      *
      * @param string|int $shardId
-     *
-     * @return \Doctrine\DBAL\Driver\Connection
      */
-    protected function connectTo($shardId)
+    protected function connectTo($shardId) : DriverConnection
     {
         $params = $this->getParams();
 
@@ -226,10 +188,8 @@ protected function connectTo($shardId)
 
     /**
      * @param string|int|null $shardId
-     *
-     * @return bool
      */
-    public function isConnected($shardId = null)
+    public function isConnected($shardId = null) : bool
     {
         if ($shardId === null) {
             return $this->_conn !== null;
@@ -238,10 +198,7 @@ public function isConnected($shardId = null)
         return isset($this->activeConnections[$shardId]);
     }
 
-    /**
-     * @return void
-     */
-    public function close()
+    public function close() : void
     {
         $this->_conn             = null;
         $this->activeConnections = [];
diff --git a/tests/Doctrine/Tests/DBAL/ConnectionTest.php b/tests/Doctrine/Tests/DBAL/ConnectionTest.php
index 53767076ff5..ef7652d821c 100644
--- a/tests/Doctrine/Tests/DBAL/ConnectionTest.php
+++ b/tests/Doctrine/Tests/DBAL/ConnectionTest.php
@@ -38,13 +38,13 @@ class ConnectionTest extends DbalTestCase
     /** @var Connection */
     private $connection;
 
-    /** @var string[] */
+    /** @var array<string, mixed> */
     protected $params = [
         'driver' => 'pdo_mysql',
         'host' => 'localhost',
         'user' => 'root',
         'password' => 'password',
-        'port' => '1234',
+        'port' => 1234,
     ];
 
     protected function setUp() : void
@@ -114,26 +114,6 @@ public function testGetConfiguration() : void
         self::assertInstanceOf(Configuration::class, $config);
     }
 
-    public function testGetHost() : void
-    {
-        self::assertEquals('localhost', $this->connection->getHost());
-    }
-
-    public function testGetPort() : void
-    {
-        self::assertEquals('1234', $this->connection->getPort());
-    }
-
-    public function testGetUsername() : void
-    {
-        self::assertEquals('root', $this->connection->getUsername());
-    }
-
-    public function testGetPassword() : void
-    {
-        self::assertEquals('password', $this->connection->getPassword());
-    }
-
     public function testGetDriver() : void
     {
         self::assertInstanceOf(\Doctrine\DBAL\Driver\PDOMySql\Driver::class, $this->connection->getDriver());
diff --git a/tests/Doctrine/Tests/DBAL/Functional/Driver/OCI8/OCI8ConnectionTest.php b/tests/Doctrine/Tests/DBAL/Functional/Driver/OCI8/OCI8ConnectionTest.php
index 4aaa091dbe5..e76cac08b00 100644
--- a/tests/Doctrine/Tests/DBAL/Functional/Driver/OCI8/OCI8ConnectionTest.php
+++ b/tests/Doctrine/Tests/DBAL/Functional/Driver/OCI8/OCI8ConnectionTest.php
@@ -49,6 +49,6 @@ public function testLastInsertIdAcceptsFqn() : void
         $schema   = $this->connection->getDatabase();
         $sequence = $platform->getIdentitySequenceName($schema . '.DBAL2595', 'id');
 
-        self::assertSame(1, $this->driverConnection->lastInsertId($sequence));
+        self::assertEquals(1, $this->driverConnection->lastInsertId($sequence));
     }
 }
diff --git a/tests/Doctrine/Tests/DBAL/Functional/Schema/OracleSchemaManagerTest.php b/tests/Doctrine/Tests/DBAL/Functional/Schema/OracleSchemaManagerTest.php
index 01b76d2bcc9..58ba12c300f 100644
--- a/tests/Doctrine/Tests/DBAL/Functional/Schema/OracleSchemaManagerTest.php
+++ b/tests/Doctrine/Tests/DBAL/Functional/Schema/OracleSchemaManagerTest.php
@@ -237,7 +237,7 @@ public function testListTableColumnsSameTableNamesInDifferentSchemas() : void
         $otherTable->addColumn('id', Types::STRING);
         TestUtil::getTempConnection()->getSchemaManager()->dropAndCreateTable($otherTable);
 
-        $columns = $this->schemaManager->listTableColumns($table->getName(), $this->connection->getUsername());
+        $columns = $this->schemaManager->listTableColumns($table->getName(), $this->connection->getDatabase());
         self::assertCount(7, $columns);
     }
 
diff --git a/tests/Doctrine/Tests/DBAL/Functional/WriteTest.php b/tests/Doctrine/Tests/DBAL/Functional/WriteTest.php
index bce41d82afc..fc784a4b608 100644
--- a/tests/Doctrine/Tests/DBAL/Functional/WriteTest.php
+++ b/tests/Doctrine/Tests/DBAL/Functional/WriteTest.php
@@ -190,7 +190,8 @@ public function testLastInsertIdNoSequenceGiven() : void
             $this->markTestSkipped("Test only works consistently on platforms that support sequences and don't support identity columns.");
         }
 
-        self::assertFalse($this->lastInsertId());
+        $this->expectException(DriverException::class);
+        $this->lastInsertId();
     }
 
     /**
diff --git a/tests/Doctrine/Tests/DBAL/Schema/DB2SchemaManagerTest.php b/tests/Doctrine/Tests/DBAL/Schema/DB2SchemaManagerTest.php
index bcf2622b295..b0d4de5f265 100644
--- a/tests/Doctrine/Tests/DBAL/Schema/DB2SchemaManagerTest.php
+++ b/tests/Doctrine/Tests/DBAL/Schema/DB2SchemaManagerTest.php
@@ -33,14 +33,10 @@ protected function setUp() : void
         $platform     = $this->createMock(DB2Platform::class);
         $this->conn   = $this
             ->getMockBuilder(Connection::class)
-            ->setMethods(['fetchAll', 'getUsername'])
+            ->setMethods(['fetchAll'])
             ->setConstructorArgs([['platform' => $platform], $driverMock, new Configuration(), $eventManager])
             ->getMock();
 
-        $this->conn->expects($this->any())
-            ->method('getUsername')
-            ->willReturn('db2inst1');
-
         $this->manager = new DB2SchemaManager($this->conn);
     }
 
diff --git a/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardConnectionTest.php b/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardConnectionTest.php
index 9569ef55d6e..1f56361668d 100644
--- a/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardConnectionTest.php
+++ b/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardConnectionTest.php
@@ -243,80 +243,4 @@ public function testGetParamsOverride() : void
             'host' => 'foo',
         ], $conn->getParams());
     }
-
-    public function testGetHostOverride() : void
-    {
-        $conn = DriverManager::getConnection([
-            'wrapperClass' => PoolingShardConnection::class,
-            'driver' => 'pdo_sqlite',
-            'host' => 'localhost',
-            'global' => ['memory' => true],
-            'shards' => [
-                ['id' => 1, 'memory' => true, 'host' => 'foo'],
-            ],
-            'shardChoser' => MultiTenantShardChoser::class,
-        ]);
-
-        self::assertEquals('localhost', $conn->getHost());
-
-        $conn->connect(1);
-        self::assertEquals('foo', $conn->getHost());
-    }
-
-    public function testGetPortOverride() : void
-    {
-        $conn = DriverManager::getConnection([
-            'wrapperClass' => PoolingShardConnection::class,
-            'driver' => 'pdo_sqlite',
-            'port' => 3306,
-            'global' => ['memory' => true],
-            'shards' => [
-                ['id' => 1, 'memory' => true, 'port' => 3307],
-            ],
-            'shardChoser' => MultiTenantShardChoser::class,
-        ]);
-
-        self::assertEquals(3306, $conn->getPort());
-
-        $conn->connect(1);
-        self::assertEquals(3307, $conn->getPort());
-    }
-
-    public function testGetUsernameOverride() : void
-    {
-        $conn = DriverManager::getConnection([
-            'wrapperClass' => PoolingShardConnection::class,
-            'driver' => 'pdo_sqlite',
-            'user' => 'foo',
-            'global' => ['memory' => true],
-            'shards' => [
-                ['id' => 1, 'memory' => true, 'user' => 'bar'],
-            ],
-            'shardChoser' => MultiTenantShardChoser::class,
-        ]);
-
-        self::assertEquals('foo', $conn->getUsername());
-
-        $conn->connect(1);
-        self::assertEquals('bar', $conn->getUsername());
-    }
-
-    public function testGetPasswordOverride() : void
-    {
-        $conn = DriverManager::getConnection([
-            'wrapperClass' => PoolingShardConnection::class,
-            'driver' => 'pdo_sqlite',
-            'password' => 'foo',
-            'global' => ['memory' => true],
-            'shards' => [
-                ['id' => 1, 'memory' => true, 'password' => 'bar'],
-            ],
-            'shardChoser' => MultiTenantShardChoser::class,
-        ]);
-
-        self::assertEquals('foo', $conn->getPassword());
-
-        $conn->connect(1);
-        self::assertEquals('bar', $conn->getPassword());
-    }
 }
diff --git a/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardManagerTest.php b/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardManagerTest.php
index 3d582d9e6c8..114b27ca824 100644
--- a/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardManagerTest.php
+++ b/tests/Doctrine/Tests/DBAL/Sharding/PoolingShardManagerTest.php
@@ -48,7 +48,14 @@ private function createStaticShardChooser() : ShardChoser
     public function testSelectGlobal() : void
     {
         $conn = $this->createConnectionMock();
-        $conn->expects($this->once())->method('connect')->with($this->equalTo(0));
+        $conn->expects($this->at(0))
+            ->method('getParams')
+            ->will(
+                $this->returnValue([
+                    'shardChoser' => $this->createMock(ShardChoser::class),
+                ])
+            );
+        $conn->expects($this->at(1))->method('connect')->with($this->equalTo(0));
 
         $shardManager = new PoolingShardManager($conn);
         $shardManager->selectGlobal();