Re: limit table to one row

r == richard(dot)broersma(at)gmail(dot)com writes:

r> On Thu, Jun 4, 2009 at 1:23 PM, Brandon Metcalf
r> <brandon(at)geronimoalloys(dot)com> wrote:

r> > Got it. Currently, it doesn't have a column for an ID, but I can add
r> > one if this is the only way.

r> Actually any column with a unique index on it will work. It doesn't
r> have to be primary key or even a serial id.

r> ANSI-SQL 92 allows for the following syntax:

r> CONSTRAINT Only_one_row
r> CHECK( 1 >= (SELECT COUNT(*) FROM _this_table;));

r> However, I have yet to find a RDBMS (PostgreSQL included) that
r> supports select statements in a table's check constraint.

I had thought about a subquery in the constraint, but as you say, that
didn't work.

Thanks for the help.

--
Brandon