R: Quote literal strings

dbQuoteString {DBI} | R Documentation

## Quote literal strings

### Description

Call this method to generate a string that is suitable for use in a query as a string literal, to make sure that you generate valid SQL and avoid SQL injection.

### Usage

    dbQuoteString(conn, x, ...)

### Arguments

`conn` | A subclass of DBIConnection, representing an active connection to an DBMS.
`x` | A character vector to quote as string.
`...` | Other arguments passed on to methods.

### Value

`dbQuoteString()` returns an object that can be coerced to character, of the same length as the input. For an empty character vector this function returns a length-0 object.

When passing the returned object again to `dbQuoteString()` as `x` argument, it is returned unchanged. Passing objects of class SQL should also return them unchanged. (For backends it may be most convenient to return SQL objects to achieve this behavior, but this is not required.)

### Specification

The returned expression can be used in a `SELECT ...` query, and for any scalar character `x` the value of `dbGetQuery(paste0("SELECT ", dbQuoteString(x)))[[1]]` must be identical to `x`, even if `x` contains spaces, quotes (single or double), backticks, or newlines (in any combination) or is itself the result of a `dbQuoteString()` call coerced back to character (even repeatedly). If `x` is `NA`, the result must merely satisfy `is.na()`. The strings `"NA"` or `"NULL"` are not treated specially.

`NA` should be translated to an unquoted SQL `NULL`, so that the query `SELECT * FROM (SELECT 1) a WHERE ... IS NULL` returns one row.

### See Also

Other DBIResult generics: `DBIResult-class`, `dbBind`, `dbClearResult`, `dbColumnInfo`, `dbFetch`, `dbGetInfo`, `dbGetRowCount`, `dbGetRowsAffected`, `dbGetStatement`, `dbHasCompleted`, `dbIsValid`, `dbQuoteIdentifier`

### Examples

    # Quoting ensures that arbitrary input is safe for use in a query
    name <- "Robert'); DROP TABLE Students;--"
    dbQuoteString(ANSI(), name)

    # NAs become NULL
    dbQuoteString(ANSI(), c("x", NA))

    # SQL vectors are always passed through as is
    var_name <- SQL("select")
    var_name
    dbQuoteString(ANSI(), var_name)

    # This mechanism is used to prevent double escaping
    dbQuoteString(ANSI(), dbQuoteString(ANSI(), name))

[Package DBI version 0.6-1 Index]