Re: Evaluate only one CASE WHEN in a select - Mailing list pgsql-general

dcrespo wrote:
> Hi everybody,
>
> I'm implementing something like this:
>
> SELECT
>     CASE WHEN add_numbers(t1.main_number,t2.main_number)>100
>         THEN t1.description1
>         ELSE t2.description1
>     END AS number_description1,
>     CASE WHEN add_numbers(t1.main_number,t2.main_number)>100
>         THEN t1.description2
>         ELSE t2.description2
>     END AS number_description2
> FROM table1 t1, table2 t2;
>
> Is there a way to evaluate the 'CASE WHEN' only once?

Sure, see the implementation of CASE here:

http://www.postgresql.org/docs/8.2/static/functions-conditional.html

Not sure what you are looking for, though, since your condition in both
CASEs above is exactly the same.

--
Guy Rouillier