Re: limit table to one row

r == richard.broersma@gmail.com writes:

 r> On Thu, Jun 4, 2009 at 1:23 PM, Brandon Metcalf
 r>  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