> How do other db engines handle these cases? If you like, I can check MS

SQL

> and Oracle.

btw, Oracle does not allow sub-selects in a CHECK constraint.

It does, however, check existing rows when adding the constraint.

So this fails:

ceate table t
(
i integer
);
commit;
insert into t (1);
commit;
alter table t
add constraint my_check (i < 0);


With regards,

Martijn Tonies
Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL
Server.
Upscene Productions
http://www.upscene.com