Question

Given I have table with some data… I have a query which is used to retrieve a data with complex case clause…

 SELECT row_number() over (...) as num, ... as field 1, 
    case ... as field2 
    FROM ...

Now I would like to add more complex logic, like

 SELECT row_number() over (...) as num, ... as field 1, 
    field2 * num as field2 
    FROM ...

Basically, if I type row_num + 1 as field2 Postgres returns me

ERROR: column “row_num” does not exist

How I can reference on field of query inside this query?

Answer 1

make a outer table and select field 2 in that table

Select *, num+1 as field2
from
(
   SELECT row_number() over (...) as num, ... as field1 FROM ...
) t