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Added example with native db parameters support #79

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Merged
yihui merged 1 commit into from
Apr 22, 2021
Merged

Added example with native db parameters support #79

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38 changes: 35 additions & 3 deletions 115-engine-sql.Rmd
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Original file line number Diff line number Diff line change
Expand Up @@ -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}
Expand All @@ -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
```
Expand Down
62 changes: 47 additions & 15 deletions 115-engine-sql.md
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Original file line number Diff line number Diff line change
Expand Up @@ -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
```
Expand All @@ -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
```


Expand All @@ -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