Re: default value based on select

Volkan YAZICI <yazicivo@xxxxxxxxxx> · Sat, 05 Apr 2008 13:21:45 +0300

On Sat, 5 Apr 2008, Pedro Doria Meunier <pdoria@xxxxxxxxxxxxxx> writes:
> Is it possible to have a table's column default value set to some form of 
> select?

AFAIK, you cannot provide sub-selects in the default values of a
field. E.g.

  CREATE TABLE foo (bar int DEFAULTS (SELECT ...), ...);

For this, I know two solutions:

1. You can create an SQL function that issues the related sub-select and
   call this function as the default value of the column.

2. Create a BEFORE INSERT/UPDATE trigger that issues the related
   sub-select if related column appears to be un-specified.

Regards.