From: | Rob Richardson <RDRichardson(at)rad-con(dot)com> |
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To: | "pgsql-novice(at)postgresql(dot)org" <pgsql-novice(at)postgresql(dot)org> |
Subject: | How can I re-use an expression in a SELECT? |
Date: | 2012-07-06 13:04:57 |
Message-ID: | 67D108EDFAD3C148A593E6ED7DCB4BBD1FDB3CF6@RADCONWIN2K8PDC.radcon.local |
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Lists: | pgsql-novice |
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?
Thanks very much!
RobR
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