/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

0 vote165 views1 answer
Get last inserted primary key
SQL
0 vote125 views1 answer
Error: SAP DBTech JDBC: [258]: insufficient privilege: Detailed info for this error can be found with guid '87813FAA56439F48BD60812F3EBEC5A4'
SQL
1 vote120 views1 answer
Where to locate set password for mysql
SQL
2 votes192 views1 answer
Postgresql group by month and year
SQL
16 votes125 views3 answers
Update table from another table
SQL
9 votes111 views2 answers
Default number in sql
SQL
1 vote120 views1 answer
Mariadb case switch
SQL
0 vote114 views1 answer
Sql server cannot create database diagram
SQL
1 vote77 views1 answer
Mysql show attributes of a table
SQL
0 vote121 views1 answer
Get initial in sql
SQL