How to write a constraint concerning a max number of rows in PostgreSQL?

11:58 16 Nov 2009

I've got a table user(id INT ...) and a table photo(id BIGINT, owner INT). owner is a reference on user(id).

I'd like to add a constraint to the table photo that would prevent more than let's say 10 photos to enter the database for each users.

What's the best way of writing this?

sql postgresql constraints