Editing Transact-SQL (section)

==Flow control==
Keywords for flow control in Transact-SQL include <code>BEGIN</code> and <code>END</code>, <code>BREAK</code>, <code>CONTINUE</code>, <code>GOTO</code>, <code>IF</code> and <code>ELSE</code>, <code>RETURN</code>, <code>WAITFOR</code>, and <code>WHILE</code>.

<code>IF</code> and <code>ELSE</code> allow conditional execution. This batch statement will print "It is the weekend" if the current date is a weekend day, or "It is a weekday" if the current date is a weekday.  (Note: This code assumes that Sunday is configured as the first day of the week in the <code>@@DATEFIRST</code> setting.)

<syntaxhighlight lang="tsql">
IF DATEPART(dw, GETDATE()) = 7 OR DATEPART(dw, GETDATE()) = 1
   PRINT 'It is the weekend.';
ELSE
   PRINT 'It is a weekday.';
</syntaxhighlight>

<code>BEGIN</code> and <code>END</code> mark a [[block of statements]]. If more than one statement is to be controlled by the conditional in the example above, we can use <code>BEGIN</code> and <code>END</code> like this:

<syntaxhighlight lang="tsql">
IF DATEPART(dw, GETDATE()) = 7 OR DATEPART(dw, GETDATE()) = 1
BEGIN
   PRINT 'It is the weekend.';
   PRINT 'Get some rest on the weekend!';
END;
ELSE
BEGIN
   PRINT 'It is a weekday.';
   PRINT 'Get to work on a weekday!';
END;
</syntaxhighlight>

<code>WAITFOR</code> will wait for a given amount of time, or until a particular time of day. The statement can be used for delays or to block execution until the set time.

<code>RETURN</code> is used to immediately return from a [[stored procedure]] or function.

<code>BREAK</code> ends the enclosing <code>WHILE</code> loop, while <code>CONTINUE</code> causes the next iteration of the loop to execute. An example of a <code>WHILE</code> loop is given below.

<syntaxhighlight lang="tsql">
DECLARE @i INT;
SET @i = 0;

WHILE @i < 5
BEGIN
   PRINT 'Hello world.';
   SET @i = @i + 1;
END;
</syntaxhighlight>