Re: Referencing function value inside CASE..WHEN

On Sun, Jun 19, 2011 at 10:45:12AM +0800, lover boi wrote:
> In the following statement, does the custom function get executed twice?
>
> SELECT
> MY_FUNCTION(...),
> CASE WHEN MY_FUNCTION(...) = '...' THEN '...' ELSE '...' END

Yes

> If so, is there a way I can make it execute once? I tried this but it gave me a "Column my_function does not exist" error.
>
> SELECT
>
> MY_FUNCTION(...) AS my_function,
>
> CASE WHEN my_function = '...' THEN '...' ELSE '...' END

You almost had it right, there is another syntax for CASE:

CASE MY_FUNCTION(...) WHEN 'foo' THEN ... WHEN 'bar' THEN ... ELSE ... END;

http://www.postgresql.org/docs/8.4/static/functions-conditional.html

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patriotism is when love of your own people comes first; nationalism,
> when hate for people other than your own comes first.
> - Charles de Gaulle