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;
DROP TABLE IF EXISTS a,b,c;
CREATE TABLE a (
id int(11) NOT NULL default '0',
name varchar(10) default NULL,
PRIMARY KEY  (id)
) TYPE=MyISAM;
INSERT INTO a VALUES (1,'aaa'),(2,'aaa'),(3,'aaa');
CREATE TABLE b (
id int(11) NOT NULL default '0',
name varchar(10) default NULL,
PRIMARY KEY  (id)
) TYPE=MyISAM;
INSERT INTO b VALUES (2,'bbb'),(3,'bbb'),(4,'bbb');
CREATE TABLE c (
id int(11) NOT NULL default '0',
mydate datetime default NULL,
PRIMARY KEY  (id)
) TYPE=MyISAM;
INSERT INTO c VALUES (1,'2002-02-04 00:00:00'),(3,'2002-05-12 00:00:00'),(5,'2002-05-12 00:00:00'),(6,'2002-06-22
00:00:00'),(7,'2002-07-22 00:00:00');
delete a,b,c from a,b,c
where to_days(now())-to_days(c.mydate)>=30
and c.id=a.id and c.id=b.id;
select * from c;
id	mydate
1	2002-02-04 00:00:00
5	2002-05-12 00:00:00
6	2002-06-22 00:00:00
7	2002-07-22 00:00:00
DROP TABLE IF EXISTS a,b,c;
drop table if exists parent, child;
CREATE TABLE IF NOT EXISTS `parent` (
`id` int(11) NOT NULL auto_increment,
`tst` text,
`tst1` text,
PRIMARY KEY  (`id`)
) TYPE=MyISAM;
CREATE TABLE IF NOT EXISTS `child` (
`ID` int(11) NOT NULL auto_increment,
`ParId` int(11) default NULL,
`tst` text,
`tst1` text,
PRIMARY KEY  (`ID`),
KEY `IX_ParId_child` (`ParId`),
FOREIGN KEY (`ParId`) REFERENCES `test.parent` (`id`)
) TYPE=MyISAM;
INSERT INTO parent(tst,tst1)
VALUES("MySQL","MySQL AB"), ("MSSQL","Microsoft"), ("ORACLE","ORACLE");
INSERT INTO child(ParId)
VALUES(1), (2), (3);
select * from child;
ID	ParId	tst	tst1
1	1	NULL	NULL
2	2	NULL	NULL
3	3	NULL	NULL
UPDATE child, parent
SET child.tst = parent.tst,
child.tst1 = parent.tst1
WHERE child.ParId = parent.Id;
select * from child;
ID	ParId	tst	tst1
1	1	MySQL	MySQL AB
2	2	MSSQL	Microsoft
3	3	ORACLE	ORACLE
drop table parent, child;