mysql bidirectional composite primary key
create trigger bi_foo before insert on foo
for each row
begin
if exists(select 1 from foo where bar1 = NEW.bar2 and bar2 = NEW.bar1)
then
signal sqlstate '50000' set message_text="Oops";
end if;
endmysql bidirectional composite primary key
CREATE TRIGGER uinsert BEFORE INSERT ON tbl_challenger
FOR EACH ROW SET NEW.u0 = LEAST(NEW.host,NEW.challenger),
NEW.u1 = GREATEST(NEW.host,NEW.challenger);
#same for update
CREATE UNIQUE INDEX uniqueness ON tbl_challenger(u0,u1);Copyright © 2021 Codeinu
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