Hi,
I am on postgresql 9.1 and use at table like
CREATE TABLE timetable(tid INTEGER PRIMARY KEY,gid INTEGER REFERENCES groups(gid),day DATE,s TIME NOT NULL,
---starte TIME NOT NULL, --- endCHECK (e > s));
Now, i need a constraint to prevent overlapping timeintervals in this
table. For this, i use a trigger:
CREATE OR REPLACE FUNCTION validate_timetable() RETURNS trigger AS $$
BEGINIF TG_OP = 'INSERT' THEN IF EXISTS( SELECT * FROM timetable WHERE gid = NEW.gid AND day = NEW.day AND s < NEW.e
ANDe > NEW.s) THEN RAISE EXCEPTION 'overlapping intervals'; END IF;ELSIF TG_OP = 'UPDATE' THEN IF EXISTS( SELECT *
FROMtimetable WHERE gid = NEW.gid AND day = NEW.day AND tid <> OLD. tid AND s < NEW.e AND e > NEW.s) THEN RAISE
EXCEPTION'overlapping intervals'; END IF;END IF;RETURN NEW;
END; $$ LANGUAGE plpgsql;
CREATE TRIGGER validate_timetable
BEFORE INSERT OR UPDATE ON timetable
FOR EACH ROW EXECUTE PROCEDURE
validate_timetable();
Is there a simpler way to check for overlapping timeintervals? I ask
this question, because i have more similar tables with similar layout
and would have to write similar functions again and again.
Thank you for any hints
Wolfgang
