Check if a parameter is null or empty in a stored procedure

Question

I know how to check if a parameter is null but i am not sure how to check if its empty ... I have these parameters and I want to check the previous parameters are empty or n

Answer 1

I sometimes use NULLIF like so...

IF NULLIF(@PreviousStartDate, '') IS NULL

There's probably no reason it's better than the way suggested by @Oded and @bluefeet, just stylistic preference.

@danihp's method is really cool but my tired old brain wouldn't go to COALESCE when I'm thinking is null or empty :-)