Re: How can I re-use an expression in a SELECT?

I understand.  Thanks very much!

RobR

----- Original Message -----

From: Rob Richardson

To: pgsql-novice@postgresql.org

Sent: Friday, July 06, 2012 2:04 PM

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?

 

Thanks very much!

 

RobR