drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t11,t12;
select (select 2);
(select 2)
2
explain select (select 2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
Warnings:
Note	1247	Select 2 was reduced during optimisation
SELECT (SELECT 1) UNION SELECT (SELECT 2);
(SELECT 1)
1
2
explain SELECT (SELECT 1) UNION SELECT (SELECT 2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
Warnings:
Note	1247	Select 2 was reduced during optimisation
Note	1247	Select 4 was reduced during optimisation
SELECT (SELECT (SELECT 0 UNION SELECT 0));
(SELECT (SELECT 0 UNION SELECT 0))
0
explain SELECT (SELECT (SELECT 0 UNION SELECT 0));
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
3	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
4	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
Warnings:
Note	1247	Select 2 was reduced during optimisation
SELECT (SELECT 1 FROM (SELECT 1) as b HAVING a=1) as a;
Reference 'a' not supported (forward reference in item list)
SELECT (SELECT 1 FROM (SELECT 1) as b HAVING b=1) as a,(SELECT 1 FROM (SELECT 1) as c HAVING a=1) as b;
Reference 'b' not supported (forward reference in item list)
SELECT (SELECT 1),MAX(1) FROM (SELECT 1) as a;
(SELECT 1)	MAX(1)
1	1
SELECT (SELECT a) as a;
Reference 'a' not supported (forward reference in item list)
EXPLAIN SELECT 1 FROM (SELECT 1 as a) as b  HAVING (SELECT a)=1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	<derived2>	system	NULL	NULL	NULL	NULL	1	
3	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
2	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
SELECT 1 FROM (SELECT 1 as a) as b HAVING (SELECT a)=1;
1
1
SELECT (SELECT 1), a;
Unknown column 'a' in 'field list'
SELECT 1 as a FROM (SELECT 1) as b HAVING (SELECT a)=1;
a
1
SELECT 1 FROM (SELECT (SELECT a) b) c;
Unknown column 'a' in 'field list'
SELECT * FROM (SELECT 1 as id) b WHERE id IN (SELECT * FROM (SELECT 1 as id) c ORDER BY id);
id
1
SELECT * FROM (SELECT 1) a  WHERE 1 IN (SELECT 1,1);
Cardinality error (more/less than 1 columns)
SELECT 1 IN (SELECT 1);
1 IN (SELECT 1)
1
SELECT 1 FROM (SELECT 1 as a) b WHERE 1 IN (SELECT (SELECT a));
1
1
select (SELECT 1 FROM (SELECT 1) a PROCEDURE ANALYSE(1));
Wrong usage of PROCEDURE and subquery
SELECT 1 FROM (SELECT 1) a PROCEDURE ANALYSE((SELECT 1));
Incorrect parameters to procedure 'ANALYSE'
SELECT (SELECT 1) as a FROM (SELECT 1) b WHERE (SELECT a) IS NULL;
a
SELECT (SELECT 1) as a FROM (SELECT 1) b WHERE (SELECT a) IS NOT NULL;
a
1
SELECT (SELECT 1,2,3) = ROW(1,2,3);
(SELECT 1,2,3) = ROW(1,2,3)
1
SELECT (SELECT 1,2,3) = ROW(1,2,1);
(SELECT 1,2,3) = ROW(1,2,1)
0
SELECT (SELECT 1,2,3) < ROW(1,2,1);
(SELECT 1,2,3) < ROW(1,2,1)
0
SELECT (SELECT 1,2,3) > ROW(1,2,1);
(SELECT 1,2,3) > ROW(1,2,1)
1
SELECT (SELECT 1,2,3) = ROW(1,2,NULL);
(SELECT 1,2,3) = ROW(1,2,NULL)
NULL
SELECT ROW(1,2,3) = (SELECT 1,2,3);
ROW(1,2,3) = (SELECT 1,2,3)
1
SELECT ROW(1,2,3) = (SELECT 1,2,1);
ROW(1,2,3) = (SELECT 1,2,1)
0
SELECT ROW(1,2,3) < (SELECT 1,2,1);
ROW(1,2,3) < (SELECT 1,2,1)
0
SELECT ROW(1,2,3) > (SELECT 1,2,1);
ROW(1,2,3) > (SELECT 1,2,1)
1
SELECT ROW(1,2,3) = (SELECT 1,2,NULL);
ROW(1,2,3) = (SELECT 1,2,NULL)
NULL
SELECT (SELECT 1.5,2,'a') = ROW(1.5,2,'a');
(SELECT 1.5,2,'a') = ROW(1.5,2,'a')
1
SELECT (SELECT 1.5,2,'a') = ROW(1.5,2,'b');
(SELECT 1.5,2,'a') = ROW(1.5,2,'b')
0
SELECT (SELECT 1.5,2,'a') = ROW('b',2,'b');
(SELECT 1.5,2,'a') = ROW('b',2,'b')
0
SELECT (SELECT 'b',2,'a') = ROW(1.5,2,'a');
(SELECT 'b',2,'a') = ROW(1.5,2,'a')
0
SELECT (SELECT 1.5,2,'a') = ROW(1.5,'c','a');
(SELECT 1.5,2,'a') = ROW(1.5,'c','a')
0
SELECT (SELECT 1.5,'c','a') = ROW(1.5,2,'a');
(SELECT 1.5,'c','a') = ROW(1.5,2,'a')
0
SELECT (SELECT * FROM (SELECT 'test' a,'test' b) a);
Cardinality error (more/less than 1 columns)
SELECT 1 as a,(SELECT a+a) b,(SELECT b);
a	b	(SELECT b)
1	2	2
create table t1 (a int);
create table t2 (a int, b int);
create table t3 (a int);
create table t4 (a int, b int);
insert into t1 values (2);
insert into t2 values (1,7),(2,7);
insert into t4 values (4,8),(3,8),(5,9);
select (select a from t1 where t1.a = a1) as a2, (select b from t2 where t2.b=a2) as a1;
Reference 'a1' not supported (forward reference in item list)
select (select a from t1 where t1.a=t2.a), a from t2;
(select a from t1 where t1.a=t2.a)	a
NULL	1
2	2
select (select a from t1 where t1.a=t2.b), a from t2;
(select a from t1 where t1.a=t2.b)	a
NULL	1
NULL	2
select (select a from t1), a from t2;
(select a from t1)	a
2	1
2	2
select (select a from t3), a from t2;
(select a from t3)	a
NULL	1
NULL	2
select * from t2 where t2.a=(select a from t1);
a	b
2	7
insert into t3 values (6),(7),(3);
select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1);
a	b
1	7
2	7
(select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1)) union (select * from t4 order by a limit 2) limit 3;
a	b
1	7
2	7
3	8
(select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1)) union (select * from t4 where t4.b=(select max(t2.a)*4 from t2) order by a);
a	b
1	7
2	7
3	8
4	8
explain (select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1)) union (select * from t4 where t4.b=(select max(t2.a)*4 from t2) order by a);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	Using filesort
3	UNION	t4	ALL	NULL	NULL	NULL	NULL	3	Using where; Using filesort
4	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	
select (select a from t3 where a<t2.a*4 order by 1 desc limit 1), a from t2;
(select a from t3 where a<t2.a*4 order by 1 desc limit 1)	a
3	1
7	2
select (select t3.a from t3 where a<8 order by 1 desc limit 1), a from 
(select * from t2 where a>1) as tt;
(select t3.a from t3 where a<8 order by 1 desc limit 1)	a
7	2
explain select (select t3.a from t3 where a<8 order by 1 desc limit 1), a from 
(select * from t2 where a>1) as tt;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	<derived3>	system	NULL	NULL	NULL	NULL	1	
3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where; Using filesort
select * from t1 where t1.a=(select t2.a from t2 where t2.b=(select max(a) from t3) order by 1 desc limit 1);
a
2
select * from t1 where t1.a=(select t2.a from t2 where t2.b=(select max(a) from t3 where t3.a > t1.a) order by 1 desc limit 1);
a
2
select * from t1 where t1.a=(select t2.a from t2 where t2.b=(select max(a) from t3 where t3.a < t1.a) order by 1 desc limit 1);
a
select b,(select avg(t2.a+(select min(t3.a) from t3 where t3.a >= t4.a)) from t2) from t4;
b	(select avg(t2.a+(select min(t3.a) from t3 where t3.a >= t4.a)) from t2)
8	7.5000
8	4.5000
9	7.5000
explain select b,(select avg(t2.a+(select min(t3.a) from t3 where t3.a >= t4.a)) from t2) from t4;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t4	ALL	NULL	NULL	NULL	NULL	3	
2	DEPENDENT SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	
3	DEPENDENT SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	Using where
select * from t3 where exists (select * from t2 where t2.b=t3.a);
a
7
select * from t3 where not exists (select * from t2 where t2.b=t3.a);
a
6
3
select * from t3 where a in (select b from t2);
a
7
select * from t3 where a not in (select b from t2);
a
6
3
select * from t3 where a = some (select b from t2);
a
7
select * from t3 where a <> any (select b from t2);
a
6
3
select * from t3 where a = all (select b from t2);
a
7
select * from t3 where a <> all (select b from t2);
a
6
3
insert into t2 values (100, 5);
select * from t3 where a < any (select b from t2);
a
6
3
select * from t3 where a < all (select b from t2);
a
3
select * from t3 where a >= any (select b from t2);
a
6
7
select * from t3 where a >= all (select b from t2);
a
7
delete from t2 where a=100;
select * from t3 where a in (select a,b from t2);
Cardinality error (more/less than 1 columns)
select * from t3 where a in (select * from t2);
Cardinality error (more/less than 1 columns)
insert into t4 values (12,7),(1,7),(10,9),(9,6),(7,6),(3,9);
select b,max(a) as ma from t4 group by b having b < (select max(t2.a)
from t2 where t2.b=t4.b);
b	ma
select b,max(a) as ma from t4 group by b having b >= (select max(t2.a)
from t2 where t2.b=t4.b);
b	ma
7	12
create table t5 (a int);
select (select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a), a from t2;
(select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a)	a
NULL	1
2	2
insert into t5 values (5);
select (select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a), a from t2;
(select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a)	a
NULL	1
2	2
insert into t5 values (2);
select (select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a), a from t2;
(select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a)	a
NULL	1
2	2
explain select (select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a), a from t2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	
2	DEPENDENT SUBQUERY	t1	system	NULL	NULL	NULL	NULL	1	
3	DEPENDENT UNION	t5	ALL	NULL	NULL	NULL	NULL	2	Using where
select (select a from t1 where t1.a=t2.a union all select a from t5 where t5.a=t2.a), a from t2;
Subselect returns more than 1 record
create table t6 (patient_uq int, clinic_uq int, index i1 (clinic_uq));
create table t7( uq int primary key, name char(25));
insert into t7 values(1,"Oblastnaia bolnitsa"),(2,"Bolnitsa Krasnogo Kresta");
insert into t6 values (1,1),(1,2),(2,2),(1,3);
select * from t6 where exists (select * from t7 where uq = clinic_uq);
patient_uq	clinic_uq
1	1
1	2
2	2
explain select * from t6 where exists (select * from t7 where uq = clinic_uq);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t6	ALL	NULL	NULL	NULL	NULL	4	Using where
2	DEPENDENT SUBQUERY	t7	eq_ref	PRIMARY	PRIMARY	4	t6.clinic_uq	1	
select * from t1 where a= (select a from t2,t4 where t2.b=t4.b);
Column: 'a' in field list is ambiguous
drop table if exists t1,t2,t3;
CREATE TABLE t3 (a varchar(20),b char(1) NOT NULL default '0');
INSERT INTO t3 VALUES ('W','a'),('A','c'),('J','b');
CREATE TABLE t2 (a varchar(20),b int NOT NULL default '0');
INSERT INTO t2 VALUES ('W','1'),('A','3'),('J','2');
CREATE TABLE t1 (a varchar(20),b date NOT NULL default '0000-00-00');
INSERT INTO t1 VALUES ('W','1732-02-22'),('A','1735-10-30'),('J','1743-04-13');
SELECT * FROM t1 WHERE b = (SELECT MIN(b) FROM t1);
a	b
W	1732-02-22
SELECT * FROM t2 WHERE b = (SELECT MIN(b) FROM t2);
a	b
W	1
SELECT * FROM t3 WHERE b = (SELECT MIN(b) FROM t3);
a	b
W	a
CREATE TABLE `t8` (
`pseudo` varchar(35) character set latin1 NOT NULL default '',
`email` varchar(60) character set latin1 NOT NULL default '',
PRIMARY KEY  (`pseudo`),
UNIQUE KEY `email` (`email`)
) TYPE=MyISAM CHARSET=latin1 ROW_FORMAT=DYNAMIC;
INSERT INTO t8 (pseudo,email) VALUES ('joce','test');
INSERT INTO t8 (pseudo,email) VALUES ('joce1','test1');
INSERT INTO t8 (pseudo,email) VALUES ('2joce1','2test1');
EXPLAIN SELECT pseudo,(SELECT email FROM t8 WHERE pseudo=(SELECT pseudo FROM t8 WHERE pseudo='joce')) FROM t8 WHERE pseudo=(SELECT pseudo FROM t8 WHERE pseudo='joce');
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t8	const	PRIMARY	PRIMARY	35	const	1	
4	SUBQUERY	t8	const	PRIMARY	PRIMARY	35		1	
2	SUBQUERY	t8	const	PRIMARY	PRIMARY	35	const	1	
3	SUBQUERY	t8	const	PRIMARY	PRIMARY	35		1	
SELECT pseudo FROM t8 WHERE pseudo=(SELECT pseudo,email FROM
t8 WHERE pseudo='joce');
Cardinality error (more/less than 1 columns)
SELECT pseudo FROM t8 WHERE pseudo=(SELECT * FROM t8 WHERE
pseudo='joce');
Cardinality error (more/less than 1 columns)
SELECT pseudo FROM t8 WHERE pseudo=(SELECT pseudo FROM t8 WHERE pseudo='joce');
pseudo
joce
SELECT pseudo FROM t8 WHERE pseudo=(SELECT pseudo FROM t8 WHERE pseudo LIKE '%joce%');
Subselect returns more than 1 record
drop table if exists t1,t2,t3,t4,t5,t6,t7,t8;
CREATE TABLE `t1` (
`topic` mediumint(8) unsigned NOT NULL default '0',
`date` date NOT NULL default '0000-00-00',
`pseudo` varchar(35) character set latin1 NOT NULL default '',
PRIMARY KEY  (`pseudo`,`date`,`topic`),
KEY `topic` (`topic`)
) TYPE=MyISAM ROW_FORMAT=DYNAMIC;
INSERT INTO t1 (topic,date,pseudo) VALUES
('43506','2002-10-02','joce'),('40143','2002-08-03','joce');
EXPLAIN SELECT DISTINCT date FROM t1 WHERE date='2002-08-03';
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	PRIMARY	41	NULL	2	Using where; Using index
EXPLAIN SELECT (SELECT DISTINCT date FROM t1 WHERE date='2002-08-03');
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
2	SUBQUERY	t1	index	NULL	PRIMARY	41	NULL	2	Using where; Using index
SELECT DISTINCT date FROM t1 WHERE date='2002-08-03';
date
2002-08-03
SELECT (SELECT DISTINCT date FROM t1 WHERE date='2002-08-03');
(SELECT DISTINCT date FROM t1 WHERE date='2002-08-03')
2002-08-03
SELECT 1 FROM t1 WHERE 1=(SELECT 1 UNION SELECT 1) UNION ALL SELECT 1;
1
1
1
1
SELECT 1 FROM t1 WHERE 1=(SELECT 1 UNION ALL SELECT 1) UNION SELECT 1;
Subselect returns more than 1 record
EXPLAIN SELECT 1 FROM t1 WHERE 1=(SELECT 1 UNION SELECT 1);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	index	NULL	topic	3	NULL	2	Using index
2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
drop table t1;
CREATE TABLE `t1` (
`numeropost` mediumint(8) unsigned NOT NULL auto_increment,
`maxnumrep` int(10) unsigned NOT NULL default '0',
PRIMARY KEY  (`numeropost`),
UNIQUE KEY `maxnumrep` (`maxnumrep`)
) TYPE=MyISAM ROW_FORMAT=FIXED;
INSERT INTO t1 (numeropost,maxnumrep) VALUES (40143,1),(43506,2);
CREATE TABLE `t2` (
`mot` varchar(30) NOT NULL default '',
`topic` mediumint(8) unsigned NOT NULL default '0',
`date` date NOT NULL default '0000-00-00',
`pseudo` varchar(35) NOT NULL default '',
PRIMARY KEY  (`mot`,`pseudo`,`date`,`topic`)
) TYPE=MyISAM ROW_FORMAT=DYNAMIC;
INSERT INTO t2 (mot,topic,date,pseudo) VALUES ('joce','40143','2002-10-22','joce'), ('joce','43506','2002-10-22','joce');
select numeropost as a FROM t1 GROUP BY (SELECT 1 FROM t1 HAVING a=1);
a
40143
SELECT numeropost,maxnumrep FROM t1 WHERE exists (SELECT 1 FROM t2 WHERE (mot='joce') AND date >= '2002-10-21' AND t1.numeropost = t2.topic) ORDER BY maxnumrep DESC LIMIT 0, 20;
numeropost	maxnumrep
43506	2
40143	1
SELECT (SELECT 1) as a FROM (SELECT 1 FROM t1 HAVING a=1) b;
Unknown column 'a' in 'having clause'
SELECT 1 IN (SELECT 1 FROM t2 HAVING a);
Unknown column 'a' in 'having clause'
SELECT * from t2 where topic IN (SELECT topic FROM t2 GROUP BY topic);
mot	topic	date	pseudo
joce	40143	2002-10-22	joce
joce	43506	2002-10-22	joce
SELECT * from t2 where topic IN (SELECT topic FROM t2 GROUP BY topic HAVING topic < 4100);
mot	topic	date	pseudo
SELECT * from t2 where topic IN (SELECT SUM(topic) FROM t1);
mot	topic	date	pseudo
SELECT * from t2 where topic = any (SELECT topic FROM t2 GROUP BY topic);
mot	topic	date	pseudo
joce	40143	2002-10-22	joce
joce	43506	2002-10-22	joce
SELECT * from t2 where topic = any (SELECT topic FROM t2 GROUP BY topic HAVING topic < 4100);
mot	topic	date	pseudo
SELECT * from t2 where topic = any (SELECT SUM(topic) FROM t1);
mot	topic	date	pseudo
SELECT * from t2 where topic = all (SELECT topic FROM t2 GROUP BY topic);
mot	topic	date	pseudo
SELECT * from t2 where topic = all (SELECT topic FROM t2 GROUP BY topic HAVING topic < 4100);
mot	topic	date	pseudo
joce	40143	2002-10-22	joce
joce	43506	2002-10-22	joce
SELECT *, topic = all (SELECT topic FROM t2 GROUP BY topic HAVING topic < 4100) from t2;
mot	topic	date	pseudo	topic = all (SELECT topic FROM t2 GROUP BY topic HAVING topic < 4100)
joce	40143	2002-10-22	joce	1
joce	43506	2002-10-22	joce	1
SELECT * from t2 where topic = all (SELECT SUM(topic) FROM t2);
mot	topic	date	pseudo
SELECT * from t2 where topic <> any (SELECT SUM(topic) FROM t2);
mot	topic	date	pseudo
joce	40143	2002-10-22	joce
joce	43506	2002-10-22	joce
SELECT * from t2 where topic IN (SELECT topic FROM t2 GROUP BY topic HAVING topic < 41000);
mot	topic	date	pseudo
joce	40143	2002-10-22	joce
SELECT * from t2 where topic = any (SELECT topic FROM t2 GROUP BY topic HAVING topic < 41000);
mot	topic	date	pseudo
joce	40143	2002-10-22	joce
SELECT * from t2 where topic = all (SELECT topic FROM t2 GROUP BY topic HAVING topic < 41000);
mot	topic	date	pseudo
joce	40143	2002-10-22	joce
SELECT *, topic = all (SELECT topic FROM t2 GROUP BY topic HAVING topic < 41000) from t2;
mot	topic	date	pseudo	topic = all (SELECT topic FROM t2 GROUP BY topic HAVING topic < 41000)
joce	40143	2002-10-22	joce	1
joce	43506	2002-10-22	joce	0
drop table t1,t2;
CREATE TABLE `t1` (
`numeropost` mediumint(8) unsigned NOT NULL auto_increment,
`maxnumrep` int(10) unsigned NOT NULL default '0',
PRIMARY KEY  (`numeropost`),
UNIQUE KEY `maxnumrep` (`maxnumrep`)
) TYPE=MyISAM ROW_FORMAT=FIXED;
INSERT INTO t1 (numeropost,maxnumrep) VALUES (1,0),(2,1);
select numeropost as a FROM t1 GROUP BY (SELECT 1 FROM t1 HAVING a=1);
Subselect returns more than 1 record
select numeropost as a FROM t1 ORDER BY (SELECT 1 FROM t1 HAVING a=1);
Subselect returns more than 1 record
drop table t1;
create table t1 (a int);
insert into t1 values (1),(2),(3);
(select * from t1) union (select * from t1) order by (select a from t1 limit 1);
a
1
2
3
drop table t1;
CREATE TABLE t1 (field char(1) NOT NULL DEFAULT 'b');
INSERT INTO t1 VALUES ();
SELECT field FROM t1 WHERE 1=(SELECT 1 UNION ALL SELECT 1 FROM (SELECT 1) a HAVING field='b');
Subselect returns more than 1 record
drop table t1;
CREATE TABLE `t1` (
`numeropost` mediumint(8) unsigned NOT NULL default '0',
`numreponse` int(10) unsigned NOT NULL auto_increment,
`pseudo` varchar(35) NOT NULL default '',
PRIMARY KEY  (`numeropost`,`numreponse`),
UNIQUE KEY `numreponse` (`numreponse`),
KEY `pseudo` (`pseudo`,`numeropost`)
) TYPE=MyISAM;
SELECT (SELECT numeropost FROM t1 HAVING numreponse=a),numreponse FROM (SELECT * FROM t1) as a;
Reference 'numreponse' not supported (forward reference in item list)
SELECT numreponse, (SELECT numeropost FROM t1 HAVING numreponse=a) FROM (SELECT * FROM t1) as a;
Unknown column 'a' in 'having clause'
SELECT numreponse, (SELECT numeropost FROM t1 HAVING numreponse=1) FROM (SELECT * FROM t1) as a;
numreponse	(SELECT numeropost FROM t1 HAVING numreponse=1)
INSERT INTO t1 (numeropost,numreponse,pseudo) VALUES (1,1,'joce'),(1,2,'joce'),(1,3,'test');
EXPLAIN SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT 1 FROM t1 WHERE numeropost='1');
Subselect returns more than 1 record
EXPLAIN SELECT MAX(numreponse) FROM t1 WHERE numeropost='1';
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
EXPLAIN SELECT numreponse FROM t1 WHERE numeropost='1' AND numreponse=(SELECT MAX(numreponse) FROM t1 WHERE numeropost='1');
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	const	PRIMARY,numreponse	PRIMARY	7	const,const	1	
2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
drop table t1;
CREATE TABLE t1 (a int(1));
INSERT INTO t1 VALUES (1);
SELECT 1 FROM (SELECT a FROM t1) b HAVING (SELECT b.a)=1;
1
1
drop table t1;
create table t1 (a int NOT NULL, b int, primary key (a));
create table t2 (a int NOT NULL, b int, primary key (a));
insert into t1 values (0, 10),(1, 11),(2, 12);
insert into t2 values (1, 21),(2, 22),(3, 23);
select * from t1;
a	b
0	10
1	11
2	12
update t1 set b= (select b from t1);
You can't specify target table 't1' for update in FROM clause
update t1 set b= (select b from t2);
Subselect returns more than 1 record
update t1 set b= (select b from t2 where t1.a = t2.a);
select * from t1;
a	b
0	NULL
1	21
2	22
drop table t1, t2;
create table t1 (a int NOT NULL, b int, primary key (a));
create table t2 (a int NOT NULL, b int, primary key (a));
insert into t1 values (0, 10),(1, 11),(2, 12);
insert into t2 values (1, 21),(2, 12),(3, 23);
select * from t1;
a	b
0	10
1	11
2	12
select * from t1 where b = (select b from t2 where t1.a = t2.a);
a	b
2	12
delete from t1 where b = (select b from t1);
You can't specify target table 't1' for update in FROM clause
delete from t1 where b = (select b from t2);
Subselect returns more than 1 record
delete from t1 where b = (select b from t2 where t1.a = t2.a);
select * from t1;
a	b
0	10
1	11
drop table t1, t2;
create table t11 (a int NOT NULL, b int, primary key (a));
create table t12 (a int NOT NULL, b int, primary key (a));
create table t2 (a int NOT NULL, b int, primary key (a));
insert into t11 values (0, 10),(1, 11),(2, 12);
insert into t12 values (33, 10),(22, 11),(2, 12);
insert into t2 values (1, 21),(2, 12),(3, 23);
select * from t11;
a	b
0	10
1	11
2	12
select * from t12;
a	b
33	10
22	11
2	12
delete t11.*, t12.* from t11,t12 where t11.a = t12.a and t11.b = (select b from t12 where t11.a = t12.a);
You can't specify target table 't12' for update in FROM clause
delete t11.*, t12.* from t11,t12 where t11.a = t12.a and t11.b = (select b from t2);
Subselect returns more than 1 record
delete t11.*, t12.* from t11,t12 where t11.a = t12.a and t11.b = (select b from t2 where t11.a = t2.a);
select * from t11;
a	b
0	10
1	11
select * from t12;
a	b
33	10
22	11
drop table t11, t12, t2;
CREATE TABLE t1 (x int);
create table t2 (a int);
create table t3 (a int);
insert into t2 values (1);
insert into t3 values (1),(2);
INSERT INTO t1 (x) VALUES ((SELECT x FROM t1));
You can't specify target table 't1' for update in FROM clause
INSERT INTO t1 (x) VALUES ((SELECT a FROM t3));
Subselect returns more than 1 record
INSERT INTO t1 (x) VALUES ((SELECT a FROM t2));
select * from t1;
x
1
insert into t2 values (1);
INSERT DELAYED INTO t1 (x) VALUES ((SELECT SUM(a) FROM t2));
select * from t1;
x
1
2
INSERT INTO t1 (x) select (SELECT SUM(a)+1 FROM t2) FROM t2;
select * from t1;
x
1
2
3
3
INSERT INTO t1 (x) select (SELECT SUM(x)+2 FROM t1) FROM t2;
You can't specify target table 't1' for update in FROM clause
INSERT DELAYED INTO t1 (x) VALUES ((SELECT SUM(x) FROM t2));
select * from t1;
x
1
2
3
3
0
drop table t1, t2, t3;
CREATE TABLE t1 (x int not null, y int, primary key (x));
create table t2 (a int);
create table t3 (a int);
insert into t2 values (1);
insert into t3 values (1),(2);
select * from t1;
x	y
replace into t1 (x, y) VALUES ((SELECT x FROM t1), (SELECT a+1 FROM t2));
You can't specify target table 't1' for update in FROM clause
replace into t1 (x, y) VALUES ((SELECT a FROM t3), (SELECT a+1 FROM t2));
Subselect returns more than 1 record
replace into t1 (x, y) VALUES ((SELECT a FROM t2), (SELECT a+1 FROM t2));
select * from t1;
x	y
1	2
replace into t1 (x, y) VALUES ((SELECT a FROM t2), (SELECT a+2 FROM t2));
select * from t1;
x	y
1	3
replace DELAYED into t1 (x, y) VALUES ((SELECT a+3 FROM t2), (SELECT a FROM t2));
select * from t1;
x	y
1	3
4	1
replace DELAYED into t1 (x, y) VALUES ((SELECT a+3 FROM t2), (SELECT a+1 FROM t2));
select * from t1;
x	y
1	3
4	2
replace LOW_PRIORITY into t1 (x, y) VALUES ((SELECT a+1 FROM t2), (SELECT a FROM t2));
select * from t1;
x	y
1	3
4	2
2	1
drop table t1, t2, t3;
SELECT * FROM (SELECT 1) b WHERE 1 IN (SELECT *);
No tables used
CREATE TABLE t2 (id int(11) default NULL, KEY id (id)) TYPE=MyISAM CHARSET=latin1;
INSERT INTO t2 VALUES (1),(2);
SELECT * FROM t2 WHERE id IN (SELECT 1);
id
1
EXPLAIN SELECT * FROM t2 WHERE id IN (SELECT 1);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ref	id	id	5	const	1	Using where; Using index
Warnings:
Note	1247	Select 2 was reduced during optimisation
SELECT * FROM t2 WHERE id IN (SELECT 1 UNION SELECT 3);
id
1
SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
id
2
EXPLAIN SELECT * FROM t2 WHERE id IN (SELECT 1+(select 1));
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	ref	id	id	5	const	1	Using where; Using index
3	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
Warnings:
Note	1247	Select 3 was reduced during optimisation
Note	1247	Select 2 was reduced during optimisation
EXPLAIN SELECT * FROM t2 WHERE id IN (SELECT 1 UNION SELECT 3);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	index	NULL	id	5	NULL	2	Using where; Using index
2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
3	DEPENDENT UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
SELECT * FROM t2 WHERE id IN (SELECT 5 UNION SELECT 3);
id
SELECT * FROM t2 WHERE id IN (SELECT 5 UNION SELECT 2);
id
2
INSERT INTO t2 VALUES ((SELECT * FROM t2));
You can't specify target table 't2' for update in FROM clause
SELECT * FROM t2;
id
1
2
CREATE TABLE t1 (id int(11) default NULL, KEY id (id)) TYPE=MyISAM CHARSET=latin1;
INSERT INTO t1 values (1),(1);
UPDATE t2 SET id=(SELECT * FROM t1);
Subselect returns more than 1 record
drop table t2, t1;
create table t1 (a int);
insert into t1 values (1),(2),(3);
select 1 IN (SELECT * from t1);
1 IN (SELECT * from t1)
1
select 10 IN (SELECT * from t1);
10 IN (SELECT * from t1)
0
select NULL IN (SELECT * from t1);
NULL IN (SELECT * from t1)
NULL
update t1 set a=NULL where a=2;
select 1 IN (SELECT * from t1);
1 IN (SELECT * from t1)
1
select 3 IN (SELECT * from t1);
3 IN (SELECT * from t1)
1
select 10 IN (SELECT * from t1);
10 IN (SELECT * from t1)
NULL
select 1 > ALL (SELECT * from t1);
1 > ALL (SELECT * from t1)
0
select 10 > ALL (SELECT * from t1);
10 > ALL (SELECT * from t1)
NULL
select 1 > ANY (SELECT * from t1);
1 > ANY (SELECT * from t1)
NULL
select 10 > ANY (SELECT * from t1);
10 > ANY (SELECT * from t1)
1
drop table t1;
create table t1 (a varchar(20));
insert into t1 values ('A'),('BC'),('DEF');
select 'A' IN (SELECT * from t1);
'A' IN (SELECT * from t1)
1
select 'XYZS' IN (SELECT * from t1);
'XYZS' IN (SELECT * from t1)
0
select NULL IN (SELECT * from t1);
NULL IN (SELECT * from t1)
NULL
update t1 set a=NULL where a='BC';
select 'A' IN (SELECT * from t1);
'A' IN (SELECT * from t1)
1
select 'DEF' IN (SELECT * from t1);
'DEF' IN (SELECT * from t1)
1
select 'XYZS' IN (SELECT * from t1);
'XYZS' IN (SELECT * from t1)
NULL
select 'A' > ALL (SELECT * from t1);
'A' > ALL (SELECT * from t1)
0
select 'XYZS' > ALL (SELECT * from t1);
'XYZS' > ALL (SELECT * from t1)
NULL
select 'A' > ANY (SELECT * from t1);
'A' > ANY (SELECT * from t1)
NULL
select 'XYZS' > ANY (SELECT * from t1);
'XYZS' > ANY (SELECT * from t1)
1
drop table t1;
create table t1 (a float);
insert into t1 values (1.5),(2.5),(3.5);
select 1.5 IN (SELECT * from t1);
1.5 IN (SELECT * from t1)
1
select 10.5 IN (SELECT * from t1);
10.5 IN (SELECT * from t1)
0
select NULL IN (SELECT * from t1);
NULL IN (SELECT * from t1)
NULL
update t1 set a=NULL where a=2.5;
select 1.5 IN (SELECT * from t1);
1.5 IN (SELECT * from t1)
1
select 3.5 IN (SELECT * from t1);
3.5 IN (SELECT * from t1)
1
select 10.5 IN (SELECT * from t1);
10.5 IN (SELECT * from t1)
NULL
select 1.5 > ALL (SELECT * from t1);
1.5 > ALL (SELECT * from t1)
0
select 10.5 > ALL (SELECT * from t1);
10.5 > ALL (SELECT * from t1)
NULL
select 1.5 > ANY (SELECT * from t1);
1.5 > ANY (SELECT * from t1)
NULL
select 10.5 > ANY (SELECT * from t1);
10.5 > ANY (SELECT * from t1)
1
explain select (select a+1) from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	
Warnings:
Note	1247	Select 2 was reduced during optimisation
select (select a+1) from t1;
(select a+1)
2.5
NULL
4.5
drop table t1;
CREATE TABLE t1 (a int(11) NOT NULL default '0', PRIMARY KEY  (a));
CREATE TABLE t2 (a int(11) default '0', INDEX (a));
INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (1),(2),(3);
SELECT t1.a, t1.a in (select t2.a from t2) FROM t1;
a	t1.a in (select t2.a from t2)
1	1
2	1
3	1
4	0
explain SELECT t1.a, t1.a in (select t2.a from t2) FROM t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	index	NULL	PRIMARY	4	NULL	4	Using index
2	DEPENDENT SUBQUERY	t2	index	a	a	5	NULL	3	Using where; Using index
drop table t1,t2;
create table t1 (a float);
select 10.5 IN (SELECT * from t1 LIMIT 1);
This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'
select 10.5 IN (SELECT * from t1 LIMIT 1 UNION SELECT 1.5);
This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'
drop table t1;
create table t1 (a int, b int, c varchar(10));
create table t2 (a int);
insert into t1 values (1,2,'a'),(2,3,'b'),(3,4,'c');
insert into t2 values (1),(2),(NULL);
select a, (select a,b,c from t1 where t1.a=t2.a) = ROW(a,2,'a'),(select c from t1 where a=t2.a)  from t2;
a	(select a,b,c from t1 where t1.a=t2.a) = ROW(a,2,'a')	(select c from t1 where a=t2.a)
1	1	a
2	0	b
NULL	NULL	NULL
select a, (select a,b,c from t1 where t1.a=t2.a) = ROW(a,3,'b'),(select c from t1 where a=t2.a) from t2;
a	(select a,b,c from t1 where t1.a=t2.a) = ROW(a,3,'b')	(select c from t1 where a=t2.a)
1	0	a
2	1	b
NULL	NULL	NULL
select a, (select a,b,c from t1 where t1.a=t2.a) = ROW(a,4,'c'),(select c from t1 where a=t2.a) from t2;
a	(select a,b,c from t1 where t1.a=t2.a) = ROW(a,4,'c')	(select c from t1 where a=t2.a)
1	0	a
2	0	b
NULL	NULL	NULL
drop table t1,t2;
create table t1 (a int, b real, c varchar(10));
insert into t1 values (1, 1, 'a'), (2,2,'b'), (NULL, 2, 'b');
select ROW(1, 1, 'a') IN (select a,b,c from t1);
ROW(1, 1, 'a') IN (select a,b,c from t1)
1
select ROW(1, 2, 'a') IN (select a,b,c from t1);
ROW(1, 2, 'a') IN (select a,b,c from t1)
NULL
select ROW(1, 1, 'a') IN (select b,a,c from t1);
ROW(1, 1, 'a') IN (select b,a,c from t1)
1
select ROW(1, 1, 'a') IN (select a,b,c from t1 where a is not null);
ROW(1, 1, 'a') IN (select a,b,c from t1 where a is not null)
1
select ROW(1, 2, 'a') IN (select a,b,c from t1 where a is not null);
ROW(1, 2, 'a') IN (select a,b,c from t1 where a is not null)
0
select ROW(1, 1, 'a') IN (select b,a,c from t1 where a is not null);
ROW(1, 1, 'a') IN (select b,a,c from t1 where a is not null)
1
select ROW(1, 1, 'a') IN (select a,b,c from t1 where c='b' or c='a');
ROW(1, 1, 'a') IN (select a,b,c from t1 where c='b' or c='a')
1
select ROW(1, 2, 'a') IN (select a,b,c from t1 where c='b' or c='a');
ROW(1, 2, 'a') IN (select a,b,c from t1 where c='b' or c='a')
NULL
select ROW(1, 1, 'a') IN (select b,a,c from t1 where c='b' or c='a');
ROW(1, 1, 'a') IN (select b,a,c from t1 where c='b' or c='a')
1
select ROW(1, 1, 'a') IN (select b,a,c from t1 limit 2);
This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'
drop table t1;
create table t1 (a int);
insert into t1 values (1);
do @a:=(SELECT a from t1);
select @a;
@a
1
set @a:=2;
set @a:=(SELECT a from t1);
select @a;
@a
1
drop table t1;
do (SELECT a from t1);
Table 'test.t1' doesn't exist
set @a:=(SELECT a from t1);
Table 'test.t1' doesn't exist
CREATE TABLE t1 (a int, KEY(a));
HANDLER t1 OPEN;
HANDLER t1 READ a=((SELECT 1));
You have an error in your SQL syntax.  Check the manual that corresponds to your MySQL server version for the right syntax to use
HANDLER t1 CLOSE;
drop table t1;
create table t1 (a int);
create table t2 (b int);
insert into t1 values (1),(2);
insert into t2 values (1);
select a from t1 where a in (select a from t1 where a in (select b from t2));
a
1
drop table t1, t2;
create table t1 (a int, b int);
create table t2 like t1;
insert into t1 values (1,2),(1,3),(1,4),(1,5);
insert into t2 values (1,2),(1,3);
select * from t1 where row(a,b) in (select a,b from t2);
a	b
1	2
1	3
drop table t1, t2;
CREATE TABLE `t1` (`i` int(11) NOT NULL default '0',PRIMARY KEY  (`i`)) TYPE=MyISAM CHARSET=latin1;
INSERT INTO t1 VALUES (1);
UPDATE t1 SET i=i+1 WHERE i=(SELECT MAX(i));
Invalid use of group function
drop table t1;
CREATE TABLE t1 (a int(1));
EXPLAIN SELECT (SELECT RAND() FROM t1) FROM t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
2	UNCACHEABLE SUBQUERY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
EXPLAIN SELECT (SELECT ENCRYPT('test') FROM t1) FROM t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
2	UNCACHEABLE SUBQUERY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
EXPLAIN SELECT (SELECT BENCHMARK(1,1) FROM t1) FROM t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
2	UNCACHEABLE SUBQUERY	t1	system	NULL	NULL	NULL	NULL	0	const row not found
drop table t1;
CREATE TABLE `t1` (
`mot` varchar(30) character set latin1 NOT NULL default '',
`topic` mediumint(8) unsigned NOT NULL default '0',
`date` date NOT NULL default '0000-00-00',
`pseudo` varchar(35) character set latin1 NOT NULL default '',
PRIMARY KEY  (`mot`,`pseudo`,`date`,`topic`),
KEY `pseudo` (`pseudo`,`date`,`topic`),
KEY `topic` (`topic`)
) TYPE=MyISAM CHARSET=latin1 ROW_FORMAT=DYNAMIC;
CREATE TABLE `t2` (
`mot` varchar(30) character set latin1 NOT NULL default '',
`topic` mediumint(8) unsigned NOT NULL default '0',
`date` date NOT NULL default '0000-00-00',
`pseudo` varchar(35) character set latin1 NOT NULL default '',
PRIMARY KEY  (`mot`,`pseudo`,`date`,`topic`),
KEY `pseudo` (`pseudo`,`date`,`topic`),
KEY `topic` (`topic`)
) TYPE=MyISAM CHARSET=latin1 ROW_FORMAT=DYNAMIC;
CREATE TABLE `t3` (
`numeropost` mediumint(8) unsigned NOT NULL auto_increment,
`maxnumrep` int(10) unsigned NOT NULL default '0',
PRIMARY KEY  (`numeropost`),
UNIQUE KEY `maxnumrep` (`maxnumrep`)
) TYPE=MyISAM CHARSET=latin1;
INSERT INTO t1 VALUES ('joce','1','','joce'),('test','2','','test');
INSERT INTO t2 VALUES ('joce','1','','joce'),('test','2','','test');
INSERT INTO t3 VALUES (1,1);
SELECT DISTINCT topic FROM t2 WHERE NOT EXISTS(SELECT * FROM t3 WHERE
numeropost=topic);
topic
2
select * from t1;
mot	topic	date	pseudo
joce	1	0000-00-00	joce
test	2	0000-00-00	test
DELETE FROM t1 WHERE topic IN (SELECT DISTINCT topic FROM t2 WHERE NOT
EXISTS(SELECT * FROM t3 WHERE numeropost=topic));
select * from t1;
mot	topic	date	pseudo
joce	1	0000-00-00	joce
drop table t1, t2, t3;
SELECT * FROM (SELECT 1 as a,(SELECT a)) a;
a	(SELECT a)
1	1
CREATE TABLE t1 SELECT * FROM (SELECT 1 as a,(SELECT 1)) a;
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` bigint(1) NOT NULL default '0',
  `(SELECT 1)` bigint(1) NOT NULL default '0'
) TYPE=MyISAM CHARSET=latin1
drop table t1;
CREATE TABLE t1 SELECT * FROM (SELECT 1 as a,(SELECT a)) a;
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` bigint(1) NOT NULL default '0',
  `(SELECT a)` bigint(1) NOT NULL default '0'
) TYPE=MyISAM CHARSET=latin1
drop table t1;
CREATE TABLE t1 SELECT * FROM (SELECT 1 as a,(SELECT a+0)) a;
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` bigint(1) NOT NULL default '0',
  `(SELECT a+0)` bigint(17) NOT NULL default '0'
) TYPE=MyISAM CHARSET=latin1
drop table t1;
CREATE TABLE t1 SELECT (SELECT 1 as a UNION SELECT 1+1 limit 1,1) as a;
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` bigint(1) NOT NULL default '0'
) TYPE=MyISAM CHARSET=latin1
drop table t1;
create table t1 (a int);
insert into t1 values (1), (2), (3);
explain select a,(select (select rand() from t1 limit 1)  from t1 limit 1)
from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	
2	UNCACHEABLE SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	3	
3	UNCACHEABLE SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	3	
drop table t1;
select t1.Continent, t2.Name, t2.Population from t1 LEFT JOIN t2 ON t1.Code = t2.Country  where t2.Population IN (select max(t2.Population) AS Population from t2, t1 where t2.Country = t1.Code group by Continent);
Table 'test.t1' doesn't exist
CREATE TABLE t1 (
ID int(11) NOT NULL auto_increment,
name char(35) NOT NULL default '',
t2 char(3) NOT NULL default '',
District char(20) NOT NULL default '',
Population int(11) NOT NULL default '0',
PRIMARY KEY  (ID)
) TYPE=MyISAM;
INSERT INTO t1 VALUES (130,'Sydney','AUS','New South Wales',3276207);
INSERT INTO t1 VALUES (131,'Melbourne','AUS','Victoria',2865329);
INSERT INTO t1 VALUES (132,'Brisbane','AUS','Queensland',1291117);
CREATE TABLE t2 (
Code char(3) NOT NULL default '',
Name char(52) NOT NULL default '',
Continent enum('Asia','Europe','North America','Africa','Oceania','Antarctica','South America') NOT NULL default 'Asia',
Region char(26) NOT NULL default '',
SurfaceArea float(10,2) NOT NULL default '0.00',
IndepYear smallint(6) default NULL,
Population int(11) NOT NULL default '0',
LifeExpectancy float(3,1) default NULL,
GNP float(10,2) default NULL,
GNPOld float(10,2) default NULL,
LocalName char(45) NOT NULL default '',
GovernmentForm char(45) NOT NULL default '',
HeadOfState char(60) default NULL,
Capital int(11) default NULL,
Code2 char(2) NOT NULL default '',
PRIMARY KEY  (Code)
) TYPE=MyISAM;
INSERT INTO t2 VALUES ('AUS','Australia','Oceania','Australia and New Zealand',7741220.00,1901,18886000,79.8,351182.00,392911.00,'Australia','Constitutional Monarchy, Federation','Elisabeth II',135,'AU');
INSERT INTO t2 VALUES ('AZE','Azerbaijan','Asia','Middle East',86600.00,1991,7734000,62.9,4127.00,4100.00,'Azärbaycan','Federal Republic','Heydär Äliyev',144,'AZ');
select t2.Continent, t1.Name, t1.Population from t2 LEFT JOIN t1 ON t2.Code = t1.t2  where t1.Population IN (select max(t1.Population) AS Population from t1, t2 where t1.t2 = t2.Code group by Continent);
Continent	Name	Population
Oceania	Sydney	3276207
drop table t1, t2;
CREATE TABLE `t1` (
`id` mediumint(8) unsigned NOT NULL auto_increment,
`pseudo` varchar(35) character set latin1 NOT NULL default '',
PRIMARY KEY  (`id`),
UNIQUE KEY `pseudo` (`pseudo`),
) TYPE=MyISAM PACK_KEYS=1 ROW_FORMAT=DYNAMIC;
INSERT INTO t1 (pseudo) VALUES ('test');
SELECT 0 IN (SELECT 1 FROM t1 a);
0 IN (SELECT 1 FROM t1 a)
0
EXPLAIN SELECT 0 IN (SELECT 1 FROM t1 a);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
INSERT INTO t1 (pseudo) VALUES ('test1');
SELECT 0 IN (SELECT 1 FROM t1 a);
0 IN (SELECT 1 FROM t1 a)
0
EXPLAIN SELECT 0 IN (SELECT 1 FROM t1 a);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
2	DEPENDENT SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
drop table t1;
CREATE TABLE `t1` (
`i` int(11) NOT NULL default '0',
PRIMARY KEY  (`i`)
) TYPE=MyISAM CHARSET=latin1;
INSERT INTO t1 VALUES (1);
UPDATE t1 SET i=i+(SELECT MAX(i) FROM (SELECT 1) t) WHERE i=(SELECT MAX(i));
Invalid use of group function
UPDATE t1 SET i=i+1 WHERE i=(SELECT MAX(i));
Invalid use of group function
UPDATE t1 SET t.i=i+(SELECT MAX(i) FROM (SELECT 1) t);
Unknown table 't' in field list
drop table t1;
CREATE TABLE t1 (
id int(11) default NULL
) TYPE=MyISAM CHARSET=latin1;
INSERT INTO t1 VALUES (1),(1),(2),(2),(1),(3);
CREATE TABLE t2 (
id int(11) default NULL,
name varchar(15) default NULL
) TYPE=MyISAM CHARSET=latin1;
INSERT INTO t2 VALUES (4,'vita'), (1,'vita'), (2,'vita'), (1,'vita');
update t1, t2 set t2.name='lenka' where t2.id in (select id from t1);
select * from t2;
id	name
4	vita
1	lenka
2	lenka
1	lenka
drop table t1,t2;
create table t1 (a int, unique index indexa (a));
insert into t1 values (-1), (-4), (-2), (NULL);
select -10 IN (select a from t1 FORCE INDEX (indexa));
-10 IN (select a from t1 FORCE INDEX (indexa))
NULL
drop table t1;
create table t1 (id int not null auto_increment primary key, salary int, key(salary));
insert into t1 (salary) values (100),(1000),(10000),(10),(500),(5000),(50000);
explain SELECT id FROM t1 where salary = (SELECT MAX(salary) FROM t1);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	ref	salary	salary	5	const	1	Using where
2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
drop table t1;