Re: How to check if an array is empty

2008/9/11 Tobias Anstett <tobias.anstett@iaas.uni-stuttgart.de>:
> Hi,
>
>
>
> in my special case I'd like to check if a XML[] is empty, because postgres
> doesn't implement any equality operators, this is not a 'simple' task.
>
>
>
> My current solution is:
>
>
>
> SELECT * FROM sometable WHERE XMLSERIALIZE(CONTENT ((XPATH('/a:bar,
> somexmlcolumn, ARRAY[ARRAY['a', 'http://foo]]))[1]) AS text)<>''
>
>
>
> But there must be a better way – maybe I missed something important - I also
> tried queries like the following:
>
>
>
> SELECT * FROM sometable WHERE (XPATH('/a:bar', somexmlcolumn,
> ARRAY[ARRAY['a', 'http://foo']]))<>('{}'::XML[])
>
>
>
> Any ideas and feedback are welcome.
>
>
>
> Cheers, Tobias

What about array_upper():

select array_upper('{}'::XML[], 1)

NULL will be returned if the array is empty in 1-dim.

--
Hitoshi Harada