drop table if exists t1,t2,t3; create table t1(id1 int not null auto_increment primary key, t char(12)); create table t2(id2 int not null, t char(12)); create table t3(id3 int not null, t char(12), index(id3)); select count(*) from t1 where id1 > 95; count(*) 5 select count(*) from t2 where id2 > 95; count(*) 25 select count(*) from t3 where id3 > 95; count(*) 250 update t1,t2,t3 set t1.t="aaa", t2.t="bbb", t3.t="cc" where t1.id1 = t2.id2 and t2.id2 = t3.id3 and t1.id1 > 90; select count(*) from t1 where t = "aaa"; count(*) 10 select count(*) from t1 where id1 > 90; count(*) 10 select count(*) from t2 where t = "bbb"; count(*) 10 select count(*) from t2 where id2 > 90; count(*) 50 select count(*) from t3 where t = "cc"; count(*) 500 select count(*) from t3 where id3 > 90; count(*) 500 delete t1.*, t2.*, t3.* from t1,t2,t3 where t1.id1 = t2.id2 and t2.id2 = t3.id3 and t1.id1 > 95; check table t1, t2, t3; Table Op Msg_type Msg_text test.t1 check status OK test.t2 check status OK test.t3 check status OK select count(*) from t1 where id1 > 95; count(*) 0 select count(*) from t2 where id2 > 95; count(*) 0 select count(*) from t3 where id3 > 95; count(*) 0 delete t1, t2, t3 from t1,t2,t3 where t1.id1 = t2.id2 and t2.id2 = t3.id3 and t1.id1 > 5; select count(*) from t1 where id1 > 5; count(*) 0 select count(*) from t2 where id2 > 5; count(*) 0 select count(*) from t3 where id3 > 5; count(*) 0 delete from t1, t2, t3 using t1,t2,t3 where t1.id1 = t2.id2 and t2.id2 = t3.id3 and t1.id1 > 0; select count(*) from t1 where id1; count(*) 0 select count(*) from t2 where id2; count(*) 0 select count(*) from t3 where id3; count(*) 0 drop table t1,t2,t3; create table t1(id1 int not null primary key, t varchar(100)) pack_keys = 1; create table t2(id2 int not null, t varchar(100), index(id2)) pack_keys = 1; delete t1 from t1,t2 where t1.id1 = t2.id2 and t1.id1 > 500; drop table t1,t2;