Re: default value returned from sql stmt

[Ken Tanzer <ken.tanzer@xxxxxxxxx>]

It depends on what exactly it is you're trying to do, and where your default is supposed to be used.  Are you wanting a single number returned?  in that case something like this

SELECT COALESCE((SELECT anum FROM t1 WHERE anum=4 [ LIMIT 1 ]),100)

that would get you back a 4 or 100 in this case.  If your anums are not unique, you'd want the "LIMIT 1" included.

Ken

On Thu, Mar 29, 2012 at 3:56 PM, David Salisbury <salisbury@xxxxxxxxx> wrote:

On 3/29/12 4:26 PM, Chris Angelico wrote:

On Fri, Mar 30, 2012 at 9:16 AM, David Salisbury<salisbury@xxxxxxxxx>  wrote:

development=# select  coalesce(anum,100) from t1 where anum = 4;

What you have there is rather different from COALESCE, as you're
looking for a case where the row completely doesn't exist. But you can
fudge it with an outer join.

Untested code:

WITH rowid AS (select 4 as anum) SELECT coalesce(anum,100) FROM rowid
LEFT JOIN t1 ON rowid.anum=t1.anum

However, you may simply want a WHERE [NOT] EXISTS predicate. There may
be other ways of achieving your goal, too.

Thanks guys!  In fact I did see the difference between no row and a null
value within a row.  But it seemed there must be a way that I was missing.

It does look though that plpg is the way to go, otherwise it just seems
to obfuscate the code, or have other possible consequences.

-ds

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