Added example with native db parameters support

115-engine-sql.Rmd

@@ -16,7 +16,12 @@ CREATE TABLE packages (id INTEGER, name TEXT)
 ```
 
 ```{sql, connection=db}
-INSERT INTO packages VALUES (1, 'readr'), (2, 'readxl'), (3, 'haven')
+INSERT INTO 
+  packages 
+VALUES 
+  (1, 'readr'), 
+  (2, 'readxl'), 
+  (3, 'haven')
 ```
 
 ```{sql connection=db}
@@ -27,15 +32,42 @@ SELECT * FROM packages
 packageReadR <- "readr"
 ```
 
+Engine can substitute named placeholders in sql that start with `?`. 
+
+Note that if you don't provide `params` as option values will be evaluated from environment
+
 ```{sql, connection=db, output.var="readrPackage"}
-SELECT * FROM packages
-WHERE name = ?packageReadR
+SELECT 
+  * 
+FROM 
+  packages
+WHERE 
+  name = ?packageReadR
 ```
 
 ```{r}
 readrPackage
 ```
 
+To use parameterised queries with native database support provide `params` in the options of the chunk.
+
+```{r setup-parameters}
+parameters <- list(package = packageReadR)
+```
+
+```{sql, connection=db, output.var="readrPackage", params=parameters}
+SELECT 
+  * 
+FROM
+  packages
+WHERE 
+  name = @package
+```
+
+```{r}
+readrPackage
+``` 
+
 ```{sql, connection=db}
 DROP TABLE IF EXISTS packages
 ```

115-engine-sql.md

@@ -18,12 +18,15 @@ DROP TABLE IF EXISTS packages
 CREATE TABLE packages (id INTEGER, name TEXT)
 ```
 
-
 ```sql
-INSERT INTO packages VALUES (1, 'readr'), (2, 'readxl'), (3, 'haven')
+INSERT INTO 
+  packages 
+VALUES 
+  (1, 'readr'), 
+  (2, 'readxl'), 
+  (3, 'haven')
 ```
 
-
 ```sql
 SELECT * FROM packages
 ```
@@ -33,21 +36,28 @@ SELECT * FROM packages
 
 Table: 3 records
 
-|id |name   |
-|:--|:------|
-|1  |readr  |
-|2  |readxl |
-|3  |haven  |
-
+| id  | name   |
+|:----|:-------|
+| 1   | readr  |
+| 2   | readxl |
+| 3   | haven  |
 
 ```r
 packageReadR <- "readr"
 ```
 
+Engine can substitute named placeholders in sql that start with `?`.
+
+Note that if you don’t provide `params` as option values will be
+evaluated from environment
 
 ```sql
-SELECT * FROM packages
-WHERE name = ?packageReadR
+SELECT 
+  * 
+FROM 
+  packages
+WHERE 
+  name = ?packageReadR
 ```
 
 
@@ -60,17 +70,39 @@ readrPackage
 ## 1  1 readr
 ```
 
+To use parameterised queries with native database support provide
+`params` in the options of the chunk.
+
+```r
+parameters <- list(package = packageReadR)
+```
 
 ```sql
-DROP TABLE IF EXISTS packages
+SELECT 
+  * 
+FROM
+  packages
+WHERE 
+  name = @package
+```
+
+```r
+readrPackage
 ```
 
 
-```sql
-SELECT * FROM packages
 ```
+##id  name
+## 1  1 readr
+```
+
 
+```sql
+DROP TABLE IF EXISTS packages
 ```
-## Error: no such table: packages
+
+```sql
+SELECT * FROM packages
 ```
 
+    ## Error: no such table: packages