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

I used alias in where like this. (INNER Query).

Select "Vendors"."VendorId", "Vendors"."Name","Result"."Total" 
From (Select "Trans"."VendorId", ("Trans"."A"+"Trans"."B"+"Trans"."C")    AS "Total"
        FROM "Trans"
    WHERE "Trans"."Year"=2014                                                
    ) As "Result"
JOIN "Vendors" ON "Result"."VendorId"="Vendors"."VendorId" 
WHERE "Vendors"."Class"='I' AND "Result"."Total" > 200