How to reuse a result column in an expression for another result column

Question

Example:

SELECT
   (SELECT SUM(...) FROM ...) as turnover,
   (SELECT SUM(...) FROM ...) as cost,
   turnover - cost as profit

Sure this is

Answer 1

this is pretty old but i ran into this problem and saw this post but didnt manage to solve my problem using the given answers so i eventually arrived at this solution :

if your query is :

SELECT
   (SELECT SUM(...) FROM ...) as turnover,
   (SELECT SUM(...) FROM ...) as cost,
   turnover - cost as profit

you can turn it into a subquery and then use the fields such as :

SELECT *,(myFields.turnover-myFields.cost) as profit 
FROM
(      
SELECT
       (SELECT SUM(...) FROM ...) as turnover,
       (SELECT SUM(...) FROM ...) as cost

) as myFields

i'm not entirely sure if this is a bad way of doing things but performance wise it seems okay for me querying over 224,000 records took 1.5 sec not sure if its later on turned into 2x of the same sub query by DB.