/SQL/Mysql bidirectional composite primary key

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;
end

Source: stackoverflow.com

Mysql 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);

Source: stackoverflow.com

Similar codes

1 vote350 views1 answer
Oracle activate job
SQL
1 vote339 views2 answers
Get date from datetime postgresql
SQL
17 votes375 views6 answers
What is cursor in sql server with example
SQL
1 vote388 views2 answers
Mysql extract number from string
SQL
4 votes360 views1 answer
Oracle error line
SQL
1 vote334 views2 answers
Sql convert datetime to year month
SQL
5 votes330 views1 answer
Oracle list packages
SQL
3 votes381 views2 answers
Check data in table mysql
SQL
0 vote346 views1 answer
Mysql config slave
SQL
1 vote350 views1 answer
Sql trigger before delete
SQL