Take non null value to do the inner join in sql

Question

I have this code here:

SELECT c.Case_Code,COALESCE(c.case1, c.case2) AS case_def,aspm.UserId
FROM Cases AS c
LEFT JOIN aspnet_Membership AS aspm
ON c.case_def = aspm.userId

And well, since there is an Alias in the On clause, it won't recognize the case_def.

What i need to do is, i need to take the non null value between case1 and case2 and i need to Left Join it as i do in my query.

How do i do this? Thanks in advance.

Answer 1

SELECT c.Case_Code,COALESCE(c.case1, c.case2) AS case_def,aspm.UserId
FROM Cases AS c
LEFT JOIN aspnet_Membership AS aspm
ON COALESCE(c.case1, c.case2) = aspm.userId

You can't specify an alias used in the select clause elsewhere in the query. However, some dbms' do accept that.