dbQuoteLiteral: Quote literal values

Description Usage Arguments Value Specification See Also Examples

Description

Call these methods to generate a string that is suitable for use in a query as a literal value of the correct type, to make sure that you generate valid SQL and protect against SQL injection attacks.

\Sexpr[results=rd,stage=render]{DBI:::methods_as_rd("dbQuoteLiteral")}

Usage

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dbQuoteLiteral(conn, x, ...)

Arguments

conn

A subclass of DBIConnection, representing an active connection to an DBMS.

x

A vector to quote as string.

...

Other arguments passed on to methods.

Value

dbQuoteLiteral() 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 dbQuoteLiteral() 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 the value of dbGetQuery(paste0("SELECT ", dbQuoteLiteral(x)))[[1]] must be equal to x for any scalar integer, numeric, string, and logical. If x is NA, the result must merely satisfy is.na(). The literals "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.

Passing a list for the x argument raises an error.

See Also

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

Examples

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

# NAs become NULL
dbQuoteLiteral(ANSI(), c(1:3, NA))

# Logicals become integers by default
dbQuoteLiteral(ANSI(), c(TRUE, FALSE, NA))

# Raw vectors become hex strings by default
dbQuoteLiteral(ANSI(), list(as.raw(1:3), NULL))

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

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

DBI documentation built on May 2, 2018, 5:04 p.m.