dbQuoteIdentifier: Quote identifiers

Description Usage Arguments Value Specification See Also Examples

Description

Call this method to generate a string that is suitable for use in a query as a column or table name, to make sure that you generate valid SQL and protect against SQL injection attacks. The inverse operation is dbUnquoteIdentifier().

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

Usage

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Arguments

conn

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

x

A character vector, SQL or Id object to quote as identifier.

...

Other arguments passed on to methods.

Value

dbQuoteIdentifier() 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. The names of the input argument are preserved in the output. When passing the returned object again to dbQuoteIdentifier() 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.)

An error is raised if the input contains NA, but not for an empty string.

Specification

Calling dbGetQuery() for a query of the format SELECT 1 AS ... returns a data frame with the identifier, unquoted, as column name. Quoted identifiers can be used as table and column names in SQL queries, in particular in queries like SELECT 1 AS ... and SELECT * FROM (SELECT 1) .... The method must use a quoting mechanism that is unambiguously different from the quoting mechanism used for strings, so that a query like SELECT ... FROM (SELECT 1 AS ...) throws an error if the column names do not match.

The method can quote column names that contain special characters such as a space, a dot, a comma, or quotes used to mark strings or identifiers, if the database supports this. In any case, checking the validity of the identifier should be performed only when executing a query, and not by dbQuoteIdentifier().

See Also

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

Examples

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

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

dbQuoteIdentifier(ANSI(), var_name)

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

Example output

<SQL> "Robert'); DROP TABLE Students;--"
<SQL> select
<SQL> select
<SQL> "Robert'); DROP TABLE Students;--"

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