Daryl Richter wrote: >> No. A constraint only applies to one row at a time. If you try to >> work around >> this by calling a function that does queries it isn't guarenteed to >> work. >> And if you are thinking of calling a function that does a query, you >> aren't >> looking at saving time over using triggers. >> >> Also, if you are going to have concurrent updates, you are going to >> need to >> do table locking to make this work. > > And, finally, you should ask yourself *why* are you doing this, given > that one of the fundamental properties of a table (relation) is that > the rows (tuples) are *unordered.* So much of what makes a relational > db a wonderful thing for storing data depends on this notion. > > If you provide an explanation of what you are trying to model, perhaps > we can help you find a better schema design.
Thanks for the insightful answers. Actually I'm just learning about and trying out CHECK constraints in Postgres (and Firebird) :-) Regards, dave ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
