Question

I want to know what does coalesce do in this case, I know it returns first non null value and I have gone through this link as well.

I want to know what does it do specifically here:

DECLARE @EMPNO NUMERIC(22,5)

SELECT @EMPNO = ''

SELECT @EMPNO = COALESCE(?, 0)

My intention in writing these statements is if @EMPNO is blank I want it to be replaced with zero instead. I’m afraid that I was able to achieve this out of these three statements.

Help me out

Answer 1

I think you have to do like this:

SELECT @EMPNO = COALESCE(@EMPNO, 0)

You know you can also write

SET @EMPNO = COALESCE(@EMPNO, 0)

You cannot set a NUMERIC to an empty varchar. You have to set it to NULL. So you full code should be like this:

DECLARE @EMPNO NUMERIC(22,5)
SELECT @EMPNO = NULL
SELECT @EMPNO = COALESCE(@EMPNO, 0)

Or you do not even need the to set the @EMPNO to NULL. When you declare a variable it is NULL by default. So the only thing you need is this:

DECLARE @EMPNO NUMERIC(22,5)
SELECT @EMPNO = COALESCE(@EMPNO, 0)

If you read on msdn it says:

Returns the first nonnull expression among its arguments.

Reference here