Havasvölgyi Ottó wrote:
Hi all,
I issued the following queries:
select substring(proname from 1 to 1) as nevresz, count(*)
from pg_proc
where nevresz = 'a'
order by nevresz
group by nevresz;
select substring(proname from 1 to 1) as nevresz, count(*)
from pg_proc
order by nevresz
group by nevresz;
The first query fails, and says that column 'nevresz' does not exist.
The second is OK.
What is the problem? I cannot use column alias in where condition?
Correct. SQL defines it that way. You could reformulate as a sub-query
if you wanted:
SELECT nevresz,count(*)
FROM
(
SELECT substring(proname from 1 to 1) as nevresz FROM pg_proc
) AS dummy
GROUP BY nevresz
ORDER BY nevresz
--
Richard Huxton
Archonet Ltd
---------------------------(end of broadcast)---------------------------
TIP 8: explain analyze is your friend
