Re: limit table to one row

On Thu, Jun 4, 2009 at 1:23 PM, Brandon Metcalf
<brandon@geronimoalloys.com> wrote:

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


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


ANSI-SQL 92 allows for the following syntax:

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

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


--
Regards,
Richard Broersma Jr.

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