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(*)
50
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;
CREATE TABLE t1 (
id int(11) NOT NULL default '0',
name varchar(10) default NULL,
PRIMARY KEY  (id)
) TYPE=MyISAM;
INSERT INTO t1 VALUES (1,'aaa'),(2,'aaa'),(3,'aaa');
CREATE TABLE t2 (
id int(11) NOT NULL default '0',
name varchar(10) default NULL,
PRIMARY KEY  (id)
) TYPE=MyISAM;
INSERT INTO t2 VALUES (2,'bbb'),(3,'bbb'),(4,'bbb');
CREATE TABLE t3 (
id int(11) NOT NULL default '0',
mydate datetime default NULL,
PRIMARY KEY  (id)
) TYPE=MyISAM;
INSERT INTO t3 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 t1,t2,t3 from t1,t2,t3 where to_days(now())-to_days(t3.mydate)>=30 and t3.id=t1.id and t3.id=t2.id;
select * from t3;
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 t1,t2,t3;
CREATE TABLE IF NOT EXISTS `t1` (
`id` int(11) NOT NULL auto_increment,
`tst` text,
`tst1` text,
PRIMARY KEY  (`id`)
) TYPE=MyISAM;
CREATE TABLE IF NOT EXISTS `t2` (
`ID` int(11) NOT NULL auto_increment,
`ParId` int(11) default NULL,
`tst` text,
`tst1` text,
PRIMARY KEY  (`ID`),
KEY `IX_ParId_t2` (`ParId`),
FOREIGN KEY (`ParId`) REFERENCES `t1` (`id`)
) TYPE=MyISAM;
INSERT INTO t1(tst,tst1) VALUES("MySQL","MySQL AB"), ("MSSQL","Microsoft"), ("ORACLE","ORACLE");
INSERT INTO t2(ParId) VALUES(1), (2), (3);
select * from t2;
ID	ParId	tst	tst1
1	1	NULL	NULL
2	2	NULL	NULL
3	3	NULL	NULL
UPDATE t2, t1 SET t2.tst = t1.tst, t2.tst1 = t1.tst1 WHERE t2.ParId = t1.Id;
select * from t2;
ID	ParId	tst	tst1
1	1	MySQL	MySQL AB
2	2	MSSQL	Microsoft
3	3	ORACLE	ORACLE
drop table t1, t2 ;
create table t1 (n numeric(10));
create table t2 (n numeric(10));
insert into t2 values (1),(2),(4),(8),(16),(32);
select * from t2 left outer join t1  using (n);
n	n
1	NULL
2	NULL
4	NULL
8	NULL
16	NULL
32	NULL
delete  t1,t2 from t2 left outer join t1  using (n);
select * from t2 left outer join t1  using (n);
n	n
drop table t1,t2 ;
create table t1 (n int(10) not null primary key, d int(10));
create table t2 (n int(10) not null primary key, d int(10));
insert into t1 values(1,1);
insert into t2 values(1,10),(2,20);
LOCK TABLES t1 write, t2 read;
DELETE t1.*, t2.* FROM t1,t2 where t1.n=t2.n;
Table 't2' was locked with a READ lock and can't be updated
UPDATE t1,t2 SET t1.d=t2.d,t2.d=30 WHERE t1.n=t2.n;
Table 't2' was locked with a READ lock and can't be updated
UPDATE t1,t2 SET t1.d=t2.d WHERE t1.n=t2.n;
Table 't2' was locked with a READ lock and can't be updated
unlock tables;
LOCK TABLES t1 write, t2 write;
UPDATE t1,t2 SET t1.d=t2.d WHERE t1.n=t2.n;
select * from t1;
n	d
1	10
DELETE t1.*, t2.* FROM t1,t2 where t1.n=t2.n;
select * from t1;
n	d
select * from t2;
n	d
2	20
unlock tables;
drop table t1,t2;
set sql_safe_updates=1;
create table t1 (n int(10), d int(10));
create table t2 (n int(10), d int(10));
insert into t1 values(1,1);
insert into t2 values(1,10),(2,20);
UPDATE t1,t2 SET t1.d=t2.d WHERE t1.n=t2.n;
You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
set sql_safe_updates=0;
drop table t1,t2;
set timestamp=1038401397;
create table t1 (n int(10) not null primary key, d int(10), t timestamp);
create table t2 (n int(10) not null primary key, d int(10), t timestamp);
insert into t1 values(1,1,NULL);
insert into t2 values(1,10,NULL),(2,20,NULL);
set timestamp=1038000000;
UPDATE t1,t2 SET t1.d=t2.d WHERE t1.n=t2.n;
select n,d,unix_timestamp(t) from t1;
n	d	unix_timestamp(t)
1	10	1038000000
select n,d,unix_timestamp(t) from t2;
n	d	unix_timestamp(t)
1	10	1038401397
2	20	1038401397
UPDATE t1,t2 SET 1=2 WHERE t1.n=t2.n;
You have an error in your SQL syntax.  Check the manual that corresponds to your MySQL server version for the right syntax to use near '1=2 WHERE t1.n=t2.n' at line 1
drop table t1,t2;
set timestamp=0;
set sql_safe_updates=0;
create table t1 (n int(10) not null primary key, d int(10));
create table t2 (n int(10) not null primary key, d int(10));
insert into t1 values(1,1), (3,3);
insert into t2 values(1,10),(2,20);
UPDATE t2 left outer join t1 on t1.n=t2.n  SET t1.d=t2.d;
select * from t1;
n	d
1	10
3	3
select * from t2;
n	d
1	10
2	20
drop table t1,t2;
create table t1 (n int(10), d int(10));
create table t2 (n int(10), d int(10));
insert into t1 values(1,1),(1,2);
insert into t2 values(1,10),(2,20);
UPDATE t1,t2 SET t1.d=t2.d,t2.d=30 WHERE t1.n=t2.n;
select * from t1;
n	d
1	10
1	10
select * from t2;
n	d
1	30
2	20
drop table t1,t2;
create table t1 (n int(10), d int(10));
create table t2 (n int(10), d int(10));
insert into t1 values(1,1),(3,2);
insert into t2 values(1,10),(1,20);
UPDATE t1,t2 SET t1.d=t2.d,t2.d=30 WHERE t1.n=t2.n;
select * from t1;
n	d
1	10
3	2
select * from t2;
n	d
1	30
1	30
UPDATE t1 a ,t2 b SET a.d=b.d,b.d=30 WHERE a.n=b.n;
select * from t1;
n	d
1	30
3	2
select * from t2;
n	d
1	30
1	30
DELETE t1, t2  FROM t1 a,t2 b where a.n=b.n;
select * from t1;
n	d
3	2
select * from t2;
n	d
drop table t1,t2;
CREATE TABLE t1 ( broj int(4) unsigned NOT NULL default '0',  naziv char(25) NOT NULL default 'NEPOZNAT',  PRIMARY KEY  (broj)) TYPE=MyISAM;
INSERT INTO t1 VALUES (1,'jedan'),(2,'dva'),(3,'tri'),(4,'xxxxxxxxxx'),(5,'a'),(10,''),(11,''),(12,''),(13,'');
CREATE TABLE t2 ( broj int(4) unsigned NOT NULL default '0',  naziv char(25) NOT NULL default 'NEPOZNAT',  PRIMARY KEY  (broj)) TYPE=MyISAM;
INSERT INTO t2 VALUES (1,'jedan'),(2,'dva'),(3,'tri'),(4,'xxxxxxxxxx'),(5,'a');
CREATE TABLE t3 ( broj int(4) unsigned NOT NULL default '0',  naziv char(25) NOT NULL default 'NEPOZNAT',  PRIMARY KEY  (broj)) TYPE=MyISAM;
INSERT INTO t3 VALUES (1,'jedan'),(2,'dva');
update t1,t2 set t1.naziv="aaaa" where t1.broj=t2.broj;
update t1,t2,t3 set t1.naziv="bbbb", t2.naziv="aaaa" where t1.broj=t2.broj and t2.broj=t3.broj;
drop table t1,t2,t3;