Subject: Re: [NOVICE] How can I re-use an expression in a SELECT?
I understand. Thanks very much!
RobR
From: Oliveiros d'Azevedo Cristina [mailto:oliveiros.cristina@marktest.pt] Sent: Friday, July 06, 2012 9:30 AM To: Rob Richardson; pgsql-novice@postgresql.org Subject: Re: [NOVICE] How can I re-use an expression in a SELECT?
I don't know any way of doing it without using a sub-query...
SELECT heat_time, cool_time, fire_date + interval '1 minute' * heat time as end_of_fire
FROM (
select charge,
case when c.rev_heat_time = 0 then c.pred_heat_time
else c.rev_heat_time
end as heat_time,
case when c.rev_cool_time = 0 then c.pred_cool_time
else c.rev_cool_time
end as cool_time
from charge c
) subquery
Surely there are more elegant ways of doing this in later versions.
Subject: [NOVICE] How can I re-use an expression in a SELECT?
Greetings!
It seems to me, from my uneducated perspective, that if I have a calculated result with a name in a SELECT query, then I ought to be able to re-use the name later in the statement:
select charge,
case when c.rev_heat_time = 0 then c.pred_heat_time
else c.rev_heat_time
end as heat_time,
case when c.rev_cool_time = 0 then c.pred_cool_time
else c.rev_cool_time
end as cool_time,
fire_date + interval '1 minute' * heat_time as end_of_fire
from charge c
Of course, that fails because heat_time cannot be used to calculate end_of_fire. I would have to repeat the case statement that defines it instead. How can I avoid repeating complicated pieces of SELECT queries like this?
