On Sat, 2011-01-15 at 15:07 -0500, Daniel Popowich wrote: > Constraint expressions can only be simple boolean expressions, so can > refer only to the column(s) of the current row you're > inserting/updating, Exclusion Constraints are a new feature in 9.0: http://www.postgresql.org/docs/9.0/static/ddl-constraints.html#DDL-CONSTRAINTS-EXCLUSION http://www.postgresql.org/docs/9.0/static/sql-createtable.html#SQL-CREATETABLE-EXCLUDE They allow you to constrain across rows, much like UNIQUE (in fact, the constraints that can be expressed by an exclusion constraint are a superset of the constraints that can be expressed by UNIQUE). > so to refer to other records (which you'll need to > do to compare destination_ids) you need to create a > function...something along the lines of this: > ... > ALTER TABLE event ADD CONSTRAINT event_overlap > CHECK(overlap_at_dest(destination_id, starts, ends)); As Tomas said, that's an unsafe thing to do. I do not recommend using a table-reading function in a check constraint. Regards, Jeff Davis -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
