How to allow only one row for a table?

Question

I have one table in which I would like only one entry. So if someone is trying to insert another row it shouldn\'t be allowed, only after someone deleted the pr

Answer 1

You should create a ON BEFORE INSERT trigger on this table. On the trigger, call a procedure that checks count(*) and when the count is 1, it returns an exception message to the user otherwise the insert is allowed to proceed.

Check this documentation for an example.