SQL ignore part of WHERE if parameter is null

Question

I have a stored procedure that fetches info from a table based on 4 parameters.

I want to get values based on the parameters, but if a parameter is NULL then that pa

Answer 1

You can use use COALESCE() function in SQL server. You don't need to use IF- Else or CASE in your statements. Here is how you can use COALESCEfunction.

SELECT Id, col1, col2, col3, col4 FROM myTable where col1 = COALESCE(NULLIF(@param1, ''), col1) and col2 = COALESCE(NULLIF(@param2, ''), col2) and col3 = COALESCE(NULLIF(@param3, ''), col3) and col4=
COALESCE(NULLIF(@param4, ''), col4)

The COALESCE function in SQL returns the first non-NULL expression among its arguments. Here for example if the @param1 is equal to null the function will return col1 which will lead to col1=col1 in the where statement which is like 1=1 meaning the condition will always be true.