Using an Alias column in the where clause in Postgresql

Question

I have a query like this:

SELECT
    jobs.*, 
    (
        CASE
            WHEN lead_informations.state IS NOT NULL THEN lead_informations.state
                   


        

Answer 1

You would need to either duplicate the case statement in the where clause, or my preference is to do something like the following:

SELECT *
FROM (
SELECT 
    jobs.*, 
    (CASE WHEN lead_informations.state IS NOT NULL THEN lead_informations.state ELSE 'NEW' END) as lead_state
FROM 
    "jobs"
    LEFT JOIN lead_informations ON lead_informations.job_id = jobs.id
    AND lead_informations.mechanic_id = 3
) q1
WHERE (lead_state = 'NEW')