Check if a parameter is null or empty in a stored procedure
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 :-)
Here is the general pattern:
IF(@PreviousStartDate IS NULL OR @PreviousStartDate = '')
'' is an empty string in SQL Server.
I use coalesce:
IF ( COALESCE( @PreviousStartDate, '' ) = '' ) ...
you can use:
IF(@PreviousStartDate IS NULL OR @PreviousStartDate = '')