tests/testthat/examples/knitr-examples/115-engine-sql.md

In parsermd: Formal Parser and Related Tools for R Markdown Documents

title: "Knit SQL Demo"

library(DBI)
db <- dbConnect(RSQLite::SQLite(), dbname = ":memory:")

DROP TABLE IF EXISTS packages

CREATE TABLE packages (id INTEGER, name TEXT)

INSERT INTO 
  packages 
VALUES 
  (1, 'readr'), 
  (2, 'readxl'), 
  (3, 'haven')

SELECT * FROM packages

Table: 3 records |id |name | |:--|:------| |1 |readr | |2 |readxl | |3 |haven |

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

SELECT 
  * 
FROM 
  packages
WHERE 
  name = ?packageReadR

readrPackage

##   id  name
## 1  1 readr

To use parameterised queries with native database support provide params in the options of the chunk.

parameters <- list(package = packageReadR)

SELECT 
  * 
FROM
  packages
WHERE 
  name = @package

readrPackage

##   id  name
## 1  1 readr

DROP TABLE IF EXISTS packages

SELECT * FROM packages

## Error: no such table: packages

parsermd documentation built on Aug. 21, 2025, 5:27 p.m.