Re: Using || operator to fold multiple columns into one

On 24/12/2009 5:04 AM, Rosser Schwarz wrote:
> On Wed, Dec 23, 2009 at 1:44 AM, Craig Ringer
> <craig(at)postnewspapers(dot)com(dot)au> wrote:
>
>> SELECT COALESCE( t_number::text, t:string::text, t_date::text, t_boolean::text) AS value;
>
> Your invocation of COALESCE is incorrect -- it is n-ary, but it
> returns its first non-NULL argument.

Yes. That was the point.

I think we're assuming the OP wants different things. You're assuming
they're trying to concatenate all fields, where more than one field in a
given record may be non-null. I'm assuming that all but one field in
each record will be null, and they want to show the "value" of the
record - in other words, they're using the record as a sort of union
type. It looks like that from the example they gave.

--
Craig Ringer