Sql server® 2012 t-sql fundamentals

Quoted Identifiers

In standard SQL, single quotes are used to delimit literal character strings (for example, ‘literal’) 

and double quotes are used to delimit irregular identifiers such as table or column names that 

include a space or start with a digit (for example, “Irregular Identifier”). In SQL Server, there’s 

a setting called QUOTED_IDENTIFIER that controls the meaning of double quotes. You can 

apply this setting either at the database level by using the ALTER DATABASE command or at 

the session level by using the SET command. When the setting is turned on, the behavior is ac-

cording to standard SQL, meaning that double quotes are used to delimit identifiers. When the 

setting is turned off, the behavior is nonstandard, and double quotes are used to delimit literal 

character strings. It is strongly recommended that you follow best practices and use standard 

behavior (with the setting on). Most database interfaces, including OLEDB and ODBC, turn this 

setting on by default.

Tip

  As an alternative to using double quotes to delimit identifiers, SQL Server 

also supports square brackets (for example, [Irregular Identifier]).

Regarding single quotes that are used to delimit literal character strings, if you want to in-

corporate a single quote character as part of the string, you need to specify two single quotes. 

For example, to express the literal abc’de, specify ‘ abc’ ‘de ‘.