Thread: Setting a default value for a select statement without results

Hi Jorge,

Look on http://www.postgresql.org/docs/8.1/static/functions-conditional.html

Thanks,
Anton

On Feb 6, 2013, at 0:23, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:

> I have an UPDATE query with the following general structure:
>
> UPDATE table1 SET (SELECT field FROM table2 WHERE conditions ORDER BY order_field LIMIT 1)
>
> Is it possible to assign a default value in case no results are returned by the SELECT statement?
>
> Respectfully,
> Jorge Maldonado

2013/2/6 JORGE MALDONADO <jorgemal1960@gmail.com>:
> I have an UPDATE query with the following general structure:
>
> UPDATE table1 SET (SELECT field FROM table2 WHERE conditions ORDER BY
> order_field LIMIT 1)
>
> Is it possible to assign a default value in case no results are returned by
> the SELECT statement?

One option would be to do something with UNION along these lines:

UPDATE table1 SET field = (SELECT field FROM table2 WHERE conditions     UNION  SELECT 'default_value' WHERE NOT EXISTS
(SELECTfield FROM table2
 
WHERE conditions )  ORDER BY order_field LIMIT 1 )

HTH

Ian Barwick

On 2013-02-06, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:
> --f46d0401fb2fcb805e04d50354b1
> Content-Type: text/plain; charset=ISO-8859-1
>
> I have an UPDATE query with the following general structure:
>
> UPDATE table1 SET (SELECT field FROM table2 WHERE conditions ORDER BY
> order_field LIMIT 1)

assuming you mean this, and you are happy with its performance.UPDATE table1 SET field1 = (SELECT field FROM table2
WHEREconditions ORDER BYorder_field LIMIT 1)
 
> Is it possible to assign a default value in case no results are returned by
> the SELECT statement?

use coalesce.
UPDATE table1 SET field1 = coalesce( (SELECT field FROM table2 WHERE conditions ORDER BYorder_field LIMIT 1) ,
default_value)
 




-- 
⚂⚃ 100% natural

Hi Jorge,

Look on http://www.postgresql.org/docs/8.1/static/functions-conditional.html

Thanks,
Anton

On Feb 6, 2013, at 0:23, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:

> I have an UPDATE query with the following general structure:
>
> UPDATE table1 SET (SELECT field FROM table2 WHERE conditions ORDER BY order_field LIMIT 1)
>
> Is it possible to assign a default value in case no results are returned by the SELECT statement?
>
> Respectfully,
> Jorge Maldonado