Re: [SQL] Letting a function work on NULL

If you are using v6.5 you can use the coalesce() function.
COALESCE returns null if and ond only its operands all evaluate to null;
otherwise it returns the value of its first nonnull operand.

hygea=> select mantello, coalesce(mantello,'null') from cani;
mantello|case
--------+----
|null
AL |AL
|null
(3 rows)

Anton de Wet ha scritto:

> I have a function that returns an integer for 100*year+month for a given
> date. Currently it croaks if the date is NULL and I would like it to
> return 0 (or even NULL).
>
> Function:
>
> create function ym (date) returns int4 as 'select
> date_part(\'year\',$1)::int4*100+date_part(\'month\',$1)::int4 ' language
> 'sql';
>
> I've tried:
> create function ym (date) returns int4 as 'select
> date_part(\'year\',$1)::int4*100+date_part(\'month\',$1)::int4 where $1 is
> not null except select 0 where $1 is null' language 'sql';
>
> (and variations with 0::int4, union instead of except, and a few desparate
> others)
>
> But all gives:
>
> select ym(NULL);
> ERROR: typeidTypeRelid: Invalid type - oid = 0
>
> Is there any way to specify an exception on the input type?
>
> Anton
>
> --------------------------------------------------------------------
> Smith's Law:
> Any sufficiently optimistic statement is indistinguishable from sarcasm.

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PostgreSQL 6.5.0 on i586-pc-linux-gnu, compiled by gcc 2.7.2.3
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Jose'