Question

I’m using a query like:

SELECT C1, C1+C2,C (C1+C2)*C3 FROM T1 WHERE C2='XX'

Now, the second column’s formula is C1+C2 and the third column is the second multiplied by C3.
So, what I want to know is, if something like this is possible:

SELECT C1,C1+C2 AS NEWC, NEWC*C3 FROM T1 WHERE C2='XX'

This query seems trivial, but actually I have a huge 4-line query over which I’d like to use a way out if there is one, since the query is getting lengthened pointlessly due to repeating the formula already stated in previous columns.

Answer 1

You can use subqueries to remove duplicate code:

SELECT C1, NEWC, NEWC*C3
  FROM (SELECT C1, C1+C2 NEWC, C3 
          FROM T1 
         WHERE C2='XX')

Sometimes, the readability can be improved by moving the subquery to the WITH clause:

WITH intermediate_result AS (
   SELECT C1, C1+C2 NEWC, C3 
     FROM T1 
    WHERE C2='XX'
)
SELECT C1, NEWC, NEWC*C3 
  FROM intermediate_result