/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

20 votes194 views4 answers
Sqlite create table if not exists
SQL
0 vote272 views1 answer
Migrations.RunSQL
SQL
0 vote187 views1 answer
Call function sql oracle
SQL
1 vote327 views2 answers
Postgres select from last 3 months
SQL
0 vote273 views1 answer
Connect google bigquery connect using sqirrel
SQL
0 vote197 views1 answer
Convert uniqueidentifier to varchar in sql
SQL
0 vote198 views1 answer
Sql last 7 days
SQL
7 votes203 views1 answer
Grant schema permissions postgres
SQL
0 vote184 views1 answer
Gcloud check sql
SQL
7 votes226 views1 answer
Oracle pagination query rownum
SQL