Select a column if other column is null
I need to select a field called ProgramID from a table and if the ProgramID is NULL then I need to select the value in the InterimProgramID from the same table and alias it as ProgramID.
How can I make a conditional SELECT statement to do this?
You need the ISNULL function.
SELECT ISNULL(a, b)
b gets selected if a is null.
Also, you can use the WHEN/THEN select option, lookup in BOL. Essentially: its c switch/case block meets SQL.
You can use either the ISNULL function or the COALESCE function. They both do pretty much the same thing, however ISNULL only takes two parameters and COALESCE takes multiple parameters (returning the first non-null it encounters). Both try the first param, then the second, (and COALESCE continues on)
DECLARE @IAMNULL VARCHAR DECLARE @IAMNOTNULL VARCHAR SET @IAMNOTNULL = 'NOT NULL' SELECT ISNULL(@IAMNULL, @IAMNOTNULL) --Output: 'NOT NULL' DECLARE @IAMNULLALSO VARCHAR SELECT COALESCE(@IAMNULL, @IAMNULLALSO, @IAMNOTNULL) --Output: 'NOT NULL'
select COALESCE ( ProgramID , InterimProgramID ) as 'ProgramID'
SELECT ProgramID FROM a_table WHERE ProgramID IS NOT NULL UNION SELECT InterimProgramID AS ProgramID FROM a_table WHERE ProgramID IS NULL;
You can also use IFNULL function
select IFNULL(ProgramId,interimId) as ProgramId
Coalesce('zzz-' + ProgramID, InterimID) as programID will still ignore ProgramID even if you have a pretext value. It's a cool little function