Hi all,
I have a select that involves a column in the result set that is expensive to
get.
I need to use the expensive column in a subsequent calculated column.
Is there a syntax to run the expensive function once only or does it just have
to be done,
blk_speed() is the expensive function.
Example of what I would like to do, does not work of course:
select
b.block,
b.p_code,
p.description,
p.blk_speed as "set",
blk_speed( b.block ) as "actual",
actual / set * 100 as "Speed %"
from block b, product p
where b.p_code = p.p_code;
This does work
select
b.block,
b.p_code,
p.description,
p.blk_speed as "set",
blk_speed( b.block ) as "actual",
blk_speed( b.block ) / ( p.blk_speed + 0.0001 ) * 100 as "Speed %"
from block b, product p
where b.p_code = p.p_code;
OR is postgres smart enough to know it only needs to get blk_speed() once.
Thanks
Allan
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