IF Statement [T-SQL]

Provides conditional execution of a Transact-SQL statement, as an alternative to the Sybase IQ IF statement.

Syntax

 IF expression
... statement
... [ ELSE [ IF expression ] statement ]...

Examples

Example 1 – Use of the Transact-SQL IF statement:

IF (SELECT max(id) FROM sysobjects) < 100
  RETURN
ELSE
  BEGIN
    PRINT 'These are the user-created objects'
    SELECT name, type, id
    FROM sysobjects
    WHERE id < 100
END

Example 2 – Use of the Transact-SQL ELSEIF statement:

BEGIN
 DECLARE @X INT
 SET @X = 1
 IF @X = 1
  PRINT '1'
  ELSEIF @X = 2
   PRINT '2'
  ELSE
   PRINT 'something else'
END

Usage

The Transact-SQL IF conditional and the ELSE conditional each control the performance of only a single SQL statement or compound statement (between the keywords BEGIN and END).

In contrast to the Sybase IQ IF statement, the Transact-SQL IF statement has no THEN. The Transact-SQL version also has no ELSEIF or END IF keywords.

When comparing variables to the single value returned by a SELECT statement inside an IF statement, you must first assign the result of the SELECT to another variable.

Note: You cannot nest the IF statement.

Standards

SQL—Transact-SQL extension to ISO/ANSI SQL grammar.
Sybase—Adaptive Server Enterprise supports the Transact-SQL IF statement.

Permissions

None