On Mon, Jul 08, 2002 at 17:49:56 +0200, Joachim Trinkwitz <[EMAIL PROTECTED]> wrote: > > Now I want to allow a user with id 123 only to insert a row in T if he > doesn't choose values from L with same 'art' and 'semester' values -- > in the examples user 123 has already chosen a kvvnr from semester > 2002ws in category 'art', so he shouldn't be allowed to insert the > values of the second row in table L.
In the database you enforce this using a unique index. The application needs to be able to handle failures when you try to insert a duplicate key. If you can't afford to have a transaction fail part way through, then anything that writes that table should do a table lock at the start of the transaction. ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
