alpav alpav - 5 months ago 44
SQL Question

How to organize infinite while loop in SQL Server?

I want to use infinite

WHILE
loop in SQL Server 2005 and use
BREAK
keyword to exit from it on certain condition.

while true
does not work, so I have to use
while 1=1
.
Is there a better way to organize infinite loop ?

I know that I can use
goto
, but
while 1=1 begin ... end
looks better structurally.

Answer

In addition to the WHILE 1 = 1 as the other answers suggest, I often add a "timeout" to my SQL "infintie" loops, as in the following example:

DECLARE @startTime datetime2(0) = GETDATE();

-- This will loop until BREAK is called, or until a timeout of 45 seconds.
WHILE (GETDATE() < DATEADD(SECOND, 45, @startTime))
BEGIN
    -- Logic goes here: The loop can be broken with the BREAK command.

    -- Throttle the loop for 2 seconds.    
    WAITFOR DELAY '00:00:02';
END

I found the above technique useful within a stored procedure that gets called from a long polling AJAX backend. Having the loop on the database-side frees the application from having to constantly hit the database to check for fresh data.

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