PostgreSQL - Aliases column and HAVING

Question

SELECT  
CASE WHEN SUM(X.Count)*3600 is null THEN  '0'  
            ELSE  
            SUM(X.Count)*3600  
       END AS PJZ,  
       X.Mass  
FROM X  
WHERE X.Mass > 2000  
HAVING ((X.Mass / PJZ * 100) - 100) >= 10;

Getting: ERROR: Column »pjz« doesn't exists.

How can I do something like this?

Answer 1

You can't use aliases in a having, and have to duplicate the statement in the having cluause. Since you only want to check for null, you could do this:

SELECT coalesce(SUM(X.Count)*3600, 0) AS PJZ, X.Mass
FROM X
WHERE X.Mass > 2000
HAVING ((X.Mass / coalesce(SUM(X.Count)*3600, 0) * 100) - 100) >= 10;