Re: can not use the column after rename

Hello,

Why I can not do something like this in Postgres.

 SELECT 1 as a , 2 as b , a + b as c ;

Regards

In a declarative language same-level cross-references are difficult to process (though admittedly not impossible).  What if you had written:

SELECT a + b AS c,  1 as a,  2 as b

If scanned in a linear (top-to-bottom) fashion A and B would not be defined at the time the “a + b” part was evaluated.

David J.