Refactor query SQL generation for standardization

src/EFCore.Relational/Query/Pipeline/QuerySqlGenerator.cs

@@ -531,19 +531,12 @@ protected virtual string GenerateOperator(SqlBinaryExpression binaryExpression)
 
         protected virtual void GenerateTop(SelectExpression selectExpression)
         {
-            if (selectExpression.Limit != null
-                && selectExpression.Offset == null)
-            {
-                _relationalCommandBuilder.Append("TOP(");
-
-                Visit(selectExpression.Limit);
-
-                _relationalCommandBuilder.Append(") ");
-            }
         }
 
         protected virtual void GenerateLimitOffset(SelectExpression selectExpression)
         {
+            // The below implements ISO SQL:2008
+
             if (selectExpression.Offset != null)
             {
                 _relationalCommandBuilder.AppendLine()
@@ -562,6 +555,15 @@ protected virtual void GenerateLimitOffset(SelectExpression selectExpression)
                     _relationalCommandBuilder.Append(" ROWS ONLY");
                 }
             }
+            else if (selectExpression.Limit != null)
+            {
+                _relationalCommandBuilder.AppendLine()
+                    .Append("FETCH FIRST ");
+
+                Visit(selectExpression.Limit);
+
+                _relationalCommandBuilder.Append(" ROWS ONLY");
+            }
         }
 
         private void GenerateList<T>(

src/EFCore.SqlServer/Extensions/SqlServerServiceCollectionExtensions.cs

@@ -90,6 +90,7 @@ public static IServiceCollection AddEntityFrameworkSqlServer([NotNull] this ISer
                 // New Query Pipeline
                 .TryAdd<IMethodCallTranslatorProvider, SqlServerMethodCallTranslatorProvider>()
                 .TryAdd<IMemberTranslatorProvider, SqlServerMemberTranslatorProvider>()
+                .TryAdd<IQuerySqlGeneratorFactory, SqlServerQuerySqlGeneratorFactory>()
                 .TryAdd<IShapedQueryOptimizerFactory, SqlServerShapedQueryOptimizerFactory>()
                 .TryAdd<IRelationalSqlTranslatingExpressionVisitorFactory, SqlServerSqlTranslatingExpressionVisitorFactory>()
 

src/EFCore.SqlServer/Query/Pipeline/SqlServerQuerySqlGenerator.cs

@@ -0,0 +1,55 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.EntityFrameworkCore.Relational.Query.Pipeline;
+using Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.SqlExpressions;
+using Microsoft.EntityFrameworkCore.Storage;
+
+namespace Microsoft.EntityFrameworkCore.SqlServer.Query.Pipeline
+{
+    public class SqlServerQuerySqlGenerator : QuerySqlGenerator
+    {
+        public SqlServerQuerySqlGenerator(
+            IRelationalCommandBuilderFactory relationalCommandBuilderFactory,
+            ISqlGenerationHelper sqlGenerationHelper)
+            : base(relationalCommandBuilderFactory, sqlGenerationHelper)
+        {
+        }
+
+        protected override void GenerateTop(SelectExpression selectExpression)
+        {
+            if (selectExpression.Limit != null
+                && selectExpression.Offset == null)
+            {
+                Sql.Append("TOP(");
+
+                Visit(selectExpression.Limit);
+
+                Sql.Append(") ");
+            }
+        }
+
+        protected override void GenerateLimitOffset(SelectExpression selectExpression)
+        {
+            // Note: For Limit without Offset, SqlServer generates TOP()
+            if (selectExpression.Offset != null)
+            {
+                Sql.AppendLine()
+                    .Append("OFFSET ");
+
+                Visit(selectExpression.Offset);
+
+                Sql.Append(" ROWS");
+
+                if (selectExpression.Limit != null)
+                {
+                    Sql.Append(" FETCH NEXT ");
+
+                    Visit(selectExpression.Limit);
+
+                    Sql.Append(" ROWS ONLY");
+                }
+            }
+        }
+    }
+}

src/EFCore.SqlServer/Query/Pipeline/SqlServerQuerySqlGeneratorFactory.cs

@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.EntityFrameworkCore.Relational.Query.Pipeline;
+using Microsoft.EntityFrameworkCore.Storage;
+
+namespace Microsoft.EntityFrameworkCore.SqlServer.Query.Pipeline
+{
+    public class SqlServerQuerySqlGeneratorFactory : QuerySqlGeneratorFactory
+    {
+        private readonly IRelationalCommandBuilderFactory _commandBuilderFactory;
+        private readonly ISqlGenerationHelper _sqlGenerationHelper;
+
+        public SqlServerQuerySqlGeneratorFactory(
+            IRelationalCommandBuilderFactory commandBuilderFactory,
+            ISqlGenerationHelper sqlGenerationHelper)
+            : base(commandBuilderFactory, sqlGenerationHelper)
+        {
+            _commandBuilderFactory = commandBuilderFactory;
+            _sqlGenerationHelper = sqlGenerationHelper;
+        }
+
+        public override QuerySqlGenerator Create()
+            => new SqlServerQuerySqlGenerator(_commandBuilderFactory, _sqlGenerationHelper);
+    }
+}

src/EFCore.Sqlite.Core/Query/Pipeline/SqliteQuerySqlGenerator.cs

@@ -24,11 +24,6 @@ protected override string GenerateOperator(SqlBinaryExpression binaryExpression)
                 ? " || "
                 : base.GenerateOperator(binaryExpression);
 
-        protected override void GenerateTop(SelectExpression selectExpression)
-        {
-            // Handled by GenerateLimitOffset
-        }
-
         protected override void GenerateLimitOffset(SelectExpression selectExpression)
         {
             Check.NotNull(selectExpression, nameof(selectExpression));

src/EFCore.Sqlite.Core/Query/Pipeline/SqliteQuerySqlGeneratorFactory2.cs → src/EFCore.Sqlite.Core/Query/Pipeline/SqliteQuerySqlGeneratorFactory.cs

@@ -21,8 +21,6 @@ public SqliteQuerySqlGeneratorFactory(
         }
 
         public override QuerySqlGenerator Create()
-        {
-            return new SqliteQuerySqlGenerator(_commandBuilderFactory, _sqlGenerationHelper);
-        }
+            => new SqliteQuerySqlGenerator(_commandBuilderFactory, _sqlGenerationHelper);
     }
 }