drop table if exists t1,t2,t3;
SELECT 1 FROM (SELECT 1) as a  GROUP BY SUM(1);
ERROR HY000: Invalid use of group function
CREATE TABLE t1 (
spID int(10) unsigned,
userID int(10) unsigned,
score smallint(5) unsigned,
lsg char(40),
date date
);
INSERT INTO t1 VALUES (1,1,1,'','0000-00-00');
INSERT INTO t1 VALUES (2,2,2,'','0000-00-00');
INSERT INTO t1 VALUES (2,1,1,'','0000-00-00');
INSERT INTO t1 VALUES (3,3,3,'','0000-00-00');
CREATE TABLE t2 (
userID int(10) unsigned NOT NULL auto_increment,
niName char(15),
passwd char(8),
mail char(50),
isAukt enum('N','Y') DEFAULT 'N',
vName char(30),
nName char(40),
adr char(60),
plz char(5),
ort char(35),
land char(20),
PRIMARY KEY (userID)
);
INSERT INTO t2 VALUES (1,'name','pass','mail','Y','v','n','adr','1','1','1');
INSERT INTO t2 VALUES (2,'name','pass','mail','Y','v','n','adr','1','1','1');
INSERT INTO t2 VALUES (3,'name','pass','mail','Y','v','n','adr','1','1','1');
INSERT INTO t2 VALUES (4,'name','pass','mail','Y','v','n','adr','1','1','1');
INSERT INTO t2 VALUES (5,'name','pass','mail','Y','v','n','adr','1','1','1');
SELECT t2.userid, MIN(t1.score) FROM t1, t2 WHERE t1.userID=t2.userID GROUP BY t2.userid;
userid	MIN(t1.score)
1	1
2	2
3	3
SELECT t2.userid, MIN(t1.score) FROM t1, t2 WHERE t1.userID=t2.userID GROUP BY t2.userid ORDER BY NULL;
userid	MIN(t1.score)
1	1
2	2
3	3
SELECT t2.userid, MIN(t1.score) FROM t1, t2 WHERE t1.userID=t2.userID AND t1.spID=2  GROUP BY t2.userid;
userid	MIN(t1.score)
1	1
2	2
SELECT t2.userid, MIN(t1.score+0.0) FROM t1, t2 WHERE t1.userID=t2.userID AND t1.spID=2  GROUP BY t2.userid;
userid	MIN(t1.score+0.0)
1	1.0
2	2.0
SELECT t2.userid, MIN(t1.score+0.0) FROM t1, t2 WHERE t1.userID=t2.userID AND t1.spID=2  GROUP BY t2.userid ORDER BY NULL;
userid	MIN(t1.score+0.0)
2	2.0
1	1.0
EXPLAIN SELECT t2.userid, MIN(t1.score+0.0) FROM t1, t2 WHERE t1.userID=t2.userID AND t1.spID=2  GROUP BY t2.userid ORDER BY NULL;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using where; Using temporary
1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.userID	1	Using index
drop table t1,t2;
CREATE TABLE t1 (
PID int(10) unsigned NOT NULL auto_increment,
payDate date DEFAULT '0000-00-00' NOT NULL,
recDate datetime DEFAULT '0000-00-00 00:00:00' NOT NULL,
URID int(10) unsigned DEFAULT '0' NOT NULL,
CRID int(10) unsigned DEFAULT '0' NOT NULL,
amount int(10) unsigned DEFAULT '0' NOT NULL,
operator int(10) unsigned,
method enum('unknown','cash','dealer','check','card','lazy','delayed','test') DEFAULT 'unknown' NOT NULL,
DIID int(10) unsigned,
reason char(1) binary DEFAULT '' NOT NULL,
code_id int(10) unsigned,
qty mediumint(8) unsigned DEFAULT '0' NOT NULL,
PRIMARY KEY (PID),
KEY URID (URID),
KEY reason (reason),
KEY method (method),
KEY payDate (payDate)
);
INSERT INTO t1 VALUES (1,'1970-01-01','1997-10-17 00:00:00',2529,1,21000,11886,'check',0,'F',16200,6);
SELECT COUNT(P.URID),SUM(P.amount),P.method, MIN(PP.recdate+0) > 19980501000000   AS IsNew FROM t1 AS P JOIN t1 as PP WHERE P.URID = PP.URID GROUP BY method,IsNew;
ERROR 42000: Can't group on 'IsNew'
drop table t1;
CREATE TABLE t1 (
cid mediumint(9) NOT NULL auto_increment,
firstname varchar(32) DEFAULT '' NOT NULL,
surname varchar(32) DEFAULT '' NOT NULL,
PRIMARY KEY (cid)
);
INSERT INTO t1 VALUES (1,'That','Guy');
INSERT INTO t1 VALUES (2,'Another','Gent');
CREATE TABLE t2 (
call_id mediumint(8) NOT NULL auto_increment,
contact_id mediumint(8) DEFAULT '0' NOT NULL,
PRIMARY KEY (call_id),
KEY contact_id (contact_id)
);
lock tables t1 read,t2 write;
INSERT INTO t2 VALUES (10,2);
INSERT INTO t2 VALUES (18,2);
INSERT INTO t2 VALUES (62,2);
INSERT INTO t2 VALUES (91,2);
INSERT INTO t2 VALUES (92,2);
SELECT cid, CONCAT(firstname, ' ', surname), COUNT(call_id) FROM t1 LEFT JOIN t2 ON cid=contact_id WHERE firstname like '%foo%' GROUP BY cid;
cid	CONCAT(firstname, ' ', surname)	COUNT(call_id)
SELECT cid, CONCAT(firstname, ' ', surname), COUNT(call_id) FROM t1 LEFT JOIN t2 ON cid=contact_id WHERE firstname like '%foo%' GROUP BY cid ORDER BY NULL;
cid	CONCAT(firstname, ' ', surname)	COUNT(call_id)
SELECT HIGH_PRIORITY cid, CONCAT(firstname, ' ', surname), COUNT(call_id) FROM t1 LEFT JOIN t2 ON cid=contact_id WHERE firstname like '%foo%' GROUP BY cid ORDER BY surname, firstname;
cid	CONCAT(firstname, ' ', surname)	COUNT(call_id)
drop table t2;
unlock tables;
drop table t1;
CREATE TABLE t1 (
bug_id mediumint(9) NOT NULL auto_increment,
groupset bigint(20) DEFAULT '0' NOT NULL,
assigned_to mediumint(9) DEFAULT '0' NOT NULL,
bug_file_loc text,
bug_severity enum('blocker','critical','major','normal','minor','trivial','enhancement') DEFAULT 'blocker' NOT NULL,
bug_status enum('','NEW','ASSIGNED','REOPENED','RESOLVED','VERIFIED','CLOSED') DEFAULT 'NEW' NOT NULL,
creation_ts datetime DEFAULT '0000-00-00 00:00:00' NOT NULL,
delta_ts timestamp,
short_desc mediumtext,
long_desc mediumtext,
op_sys enum('All','Windows 3.1','Windows 95','Windows 98','Windows NT','Windows 2000','Linux','other') DEFAULT 'All' NOT NULL,
priority enum('P1','P2','P3','P4','P5') DEFAULT 'P1' NOT NULL,
product varchar(64) DEFAULT '' NOT NULL,
rep_platform enum('All','PC','VTD-8','Other'),
reporter mediumint(9) DEFAULT '0' NOT NULL,
version varchar(16) DEFAULT '' NOT NULL,
component varchar(50) DEFAULT '' NOT NULL,
resolution enum('','FIXED','INVALID','WONTFIX','LATER','REMIND','DUPLICATE','WORKSFORME') DEFAULT '' NOT NULL,
target_milestone varchar(20) DEFAULT '' NOT NULL,
qa_contact mediumint(9) DEFAULT '0' NOT NULL,
status_whiteboard mediumtext NOT NULL,
votes mediumint(9) DEFAULT '0' NOT NULL,
PRIMARY KEY (bug_id),
KEY assigned_to (assigned_to),
KEY creation_ts (creation_ts),
KEY delta_ts (delta_ts),
KEY bug_severity (bug_severity),
KEY bug_status (bug_status),
KEY op_sys (op_sys),
KEY priority (priority),
KEY product (product),
KEY reporter (reporter),
KEY version (version),
KEY component (component),
KEY resolution (resolution),
KEY target_milestone (target_milestone),
KEY qa_contact (qa_contact),
KEY votes (votes)
);
INSERT INTO t1 VALUES (1,0,0,'','normal','','2000-02-10 09:25:12',20000321114747,'','','Linux','P1','TestProduct','PC',3,'other','TestComponent','','M1',0,'',0);
INSERT INTO t1 VALUES (9,0,0,'','enhancement','','2000-03-10 11:49:36',20000321114747,'','','All','P5','AAAAA','PC',3,'2.00 CD - Pre','BBBBBBBBBBBBB - conversion','','',0,'',0);
INSERT INTO t1 VALUES (10,0,0,'','enhancement','','2000-03-10 18:10:16',20000321114747,'','','All','P4','AAAAA','PC',3,'2.00 CD - Pre','BBBBBBBBBBBBB - conversion','','',0,'',0);
INSERT INTO t1 VALUES (7,0,0,'','critical','','2000-03-09 10:50:21',20000321114747,'','','All','P1','AAAAA','PC',3,'2.00 CD - Pre','BBBBBBBBBBBBB - generic','','',0,'',0);
INSERT INTO t1 VALUES (6,0,0,'','normal','','2000-03-09 10:42:44',20000321114747,'','','All','P2','AAAAA','PC',3,'2.00 CD - Pre','kkkkkkkkkkk lllllllllll','','',0,'',0);
INSERT INTO t1 VALUES (8,0,0,'','major','','2000-03-09 11:32:14',20000321114747,'','','All','P3','AAAAA','PC',3,'2.00 CD - Pre','kkkkkkkkkkk lllllllllll','','',0,'',0);
INSERT INTO t1 VALUES (5,0,0,'','enhancement','','2000-03-09 10:38:59',20000321114747,'','','All','P5','CCC/CCCCCC','PC',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (4,0,0,'','normal','','2000-03-08 18:32:14',20000321114747,'','','other','P2','TestProduct','Other',3,'other','TestComponent2','','',0,'',0);
INSERT INTO t1 VALUES (3,0,0,'','normal','','2000-03-08 18:30:52',20000321114747,'','','other','P2','TestProduct','Other',3,'other','TestComponent','','',0,'',0);
INSERT INTO t1 VALUES (2,0,0,'','enhancement','','2000-03-08 18:24:51',20000321114747,'','','All','P2','TestProduct','Other',4,'other','TestComponent2','','',0,'',0);
INSERT INTO t1 VALUES (11,0,0,'','blocker','','2000-03-13 09:43:41',20000321114747,'','','All','P2','CCC/CCCCCC','PC',5,'7.00','DDDDDDDDD','','',0,'',0);
INSERT INTO t1 VALUES (12,0,0,'','normal','','2000-03-13 16:14:31',20000321114747,'','','All','P2','AAAAA','PC',3,'2.00 CD - Pre','kkkkkkkkkkk lllllllllll','','',0,'',0);
INSERT INTO t1 VALUES (13,0,0,'','normal','','2000-03-15 16:20:44',20000321114747,'','','other','P2','TestProduct','Other',3,'other','TestComponent','','',0,'',0);
INSERT INTO t1 VALUES (14,0,0,'','blocker','','2000-03-15 18:13:47',20000321114747,'','','All','P1','AAAAA','PC',3,'2.00 CD - Pre','BBBBBBBBBBBBB - generic','','',0,'',0);
INSERT INTO t1 VALUES (15,0,0,'','minor','','2000-03-16 18:03:28',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','DDDDDDDDD','','',0,'',0);
INSERT INTO t1 VALUES (16,0,0,'','normal','','2000-03-16 18:33:41',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (17,0,0,'','normal','','2000-03-16 18:34:18',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (18,0,0,'','normal','','2000-03-16 18:34:56',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (19,0,0,'','enhancement','','2000-03-16 18:35:34',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (20,0,0,'','enhancement','','2000-03-16 18:36:23',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (21,0,0,'','enhancement','','2000-03-16 18:37:23',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (22,0,0,'','enhancement','','2000-03-16 18:38:16',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','Administration','','',0,'',0);
INSERT INTO t1 VALUES (23,0,0,'','normal','','2000-03-16 18:58:12',20000321114747,'','','All','P2','CCC/CCCCCC','Other',5,'7.00','DDDDDDDDD','','',0,'',0);
INSERT INTO t1 VALUES (24,0,0,'','normal','','2000-03-17 11:08:10',20000321114747,'','','All','P2','AAAAAAAA-AAA','PC',3,'2.8','Web Interface','','',0,'',0);
INSERT INTO t1 VALUES (25,0,0,'','normal','','2000-03-17 11:10:45',20000321114747,'','','All','P2','AAAAAAAA-AAA','PC',3,'2.8','Web Interface','','',0,'',0);
INSERT INTO t1 VALUES (26,0,0,'','normal','','2000-03-17 11:15:47',20000321114747,'','','All','P2','AAAAAAAA-AAA','PC',3,'2.8','Web Interface','','',0,'',0);
INSERT INTO t1 VALUES (27,0,0,'','normal','','2000-03-17 17:45:41',20000321114747,'','','All','P2','CCC/CCCCCC','PC',5,'7.00','DDDDDDDDD','','',0,'',0);
INSERT INTO t1 VALUES (28,0,0,'','normal','','2000-03-20 09:51:45',20000321114747,'','','Windows NT','P2','TestProduct','PC',8,'other','TestComponent','','',0,'',0);
INSERT INTO t1 VALUES (29,0,0,'','normal','','2000-03-20 11:15:09',20000321114747,'','','All','P5','AAAAAAAA-AAA','PC',3,'2.8','Web Interface','','',0,'',0);
CREATE TABLE t2 (
value tinytext,
program varchar(64),
initialowner tinytext NOT NULL,
initialqacontact tinytext NOT NULL,
description mediumtext NOT NULL
);
INSERT INTO t2 VALUES ('TestComponent','TestProduct','id0001','','');
INSERT INTO t2 VALUES ('BBBBBBBBBBBBB - conversion','AAAAA','id0001','','');
INSERT INTO t2 VALUES ('BBBBBBBBBBBBB - generic','AAAAA','id0001','','');
INSERT INTO t2 VALUES ('TestComponent2','TestProduct','id0001','','');
INSERT INTO t2 VALUES ('BBBBBBBBBBBBB - eeeeeeeee','AAAAA','id0001','','');
INSERT INTO t2 VALUES ('kkkkkkkkkkk lllllllllll','AAAAA','id0001','','');
INSERT INTO t2 VALUES ('Test Procedures','AAAAA','id0001','','');
INSERT INTO t2 VALUES ('Documentation','AAAAA','id0003','','');
INSERT INTO t2 VALUES ('DDDDDDDDD','CCC/CCCCCC','id0002','','');
INSERT INTO t2 VALUES ('Eeeeeeee Lite','CCC/CCCCCC','id0002','','');
INSERT INTO t2 VALUES ('Eeeeeeee Full','CCC/CCCCCC','id0002','','');
INSERT INTO t2 VALUES ('Administration','CCC/CCCCCC','id0002','','');
INSERT INTO t2 VALUES ('Distribution','CCC/CCCCCC','id0002','','');
INSERT INTO t2 VALUES ('Setup','CCC/CCCCCC','id0002','','');
INSERT INTO t2 VALUES ('Unspecified','CCC/CCCCCC','id0002','','');
INSERT INTO t2 VALUES ('Web Interface','AAAAAAAA-AAA','id0001','','');
INSERT INTO t2 VALUES ('Host communication','AAAAA','id0001','','');
select value,description,bug_id from t2 left join t1 on t2.program=t1.product and t2.value=t1.component where program="AAAAA";
value	description	bug_id
BBBBBBBBBBBBB - conversion		9
BBBBBBBBBBBBB - conversion		10
BBBBBBBBBBBBB - generic		7
BBBBBBBBBBBBB - generic		14
BBBBBBBBBBBBB - eeeeeeeee		NULL
kkkkkkkkkkk lllllllllll		6
kkkkkkkkkkk lllllllllll		8
kkkkkkkkkkk lllllllllll		12
Test Procedures		NULL
Documentation		NULL
Host communication		NULL
select value,description,COUNT(bug_id) from t2 left join t1 on t2.program=t1.product and t2.value=t1.component where program="AAAAA" group by value;
value	description	COUNT(bug_id)
BBBBBBBBBBBBB - conversion		2
BBBBBBBBBBBBB - eeeeeeeee		0
BBBBBBBBBBBBB - generic		2
Documentation		0
Host communication		0
kkkkkkkkkkk lllllllllll		3
Test Procedures		0
select value,description,COUNT(bug_id) from t2 left join t1 on t2.program=t1.product and t2.value=t1.component where program="AAAAA" group by value having COUNT(bug_id) IN (0,2);
value	description	COUNT(bug_id)
BBBBBBBBBBBBB - conversion		2
BBBBBBBBBBBBB - eeeeeeeee		0
BBBBBBBBBBBBB - generic		2
Documentation		0
Host communication		0
Test Procedures		0
drop table t1,t2;
create table t1 (foo int);
insert into t1 values (1);
select 1+1, "a",count(*) from t1 where foo in (2);
1+1	a	count(*)
2	a	0
insert into t1 values (1);
select 1+1,"a",count(*) from t1 where foo in (2);
1+1	a	count(*)
2	a	0
drop table t1;
CREATE TABLE t1 (
spID int(10) unsigned,
userID int(10) unsigned,
score smallint(5) unsigned,
key (spid),
key (score)
);
INSERT INTO t1 VALUES (1,1,1),(2,2,2),(2,1,1),(3,3,3),(4,3,3),(5,3,3),(6,3,3),(7,3,3);
explain select userid,count(*) from t1 group by userid desc;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	8	Using temporary; Using filesort
explain select userid,count(*) from t1 group by userid desc order by null;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	8	Using temporary
select userid,count(*) from t1 group by userid desc;
userid	count(*)
3	5
2	1
1	2
select userid,count(*) from t1 group by userid desc having (count(*)+1) IN (4,3);
userid	count(*)
1	2
select userid,count(*) from t1 group by userid desc having 3  IN (1,COUNT(*));
userid	count(*)
explain select spid,count(*) from t1 where spid between 1 and 2 group by spid desc;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	spID	spID	5	NULL	1	Using where; Using index
explain select spid,count(*) from t1 where spid between 1 and 2 group by spid;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	spID	spID	5	NULL	1	Using where; Using index
explain select spid,count(*) from t1 where spid between 1 and 2 group by spid order by null;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	spID	spID	5	NULL	1	Using where; Using index
select spid,count(*) from t1 where spid between 1 and 2 group by spid;
spid	count(*)
1	1
2	2
select spid,count(*) from t1 where spid between 1 and 2 group by spid desc;
spid	count(*)
2	2
1	1
explain extended select sql_big_result spid,sum(userid) from t1 group by spid desc;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	8	100.00	Using filesort
Warnings:
Note	1003	select sql_big_result `test`.`t1`.`spID` AS `spid`,sum(`test`.`t1`.`userID`) AS `sum(userid)` from `test`.`t1` group by `test`.`t1`.`spID` desc
explain select sql_big_result spid,sum(userid) from t1 group by spid desc order by null;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	8	Using filesort
select sql_big_result spid,sum(userid) from t1 group by spid desc;
spid	sum(userid)
7	3
6	3
5	3
4	3
3	3
2	3
1	1
explain select sql_big_result score,count(*) from t1 group by score desc;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	score	3	NULL	8	Using index; Using filesort
explain select sql_big_result score,count(*) from t1 group by score desc order by null;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	score	3	NULL	8	Using index; Using filesort
select sql_big_result score,count(*) from t1 group by score desc;
score	count(*)
3	5
2	1
1	2
drop table t1;
create table t1 (a date default null, b date default null);
insert t1 values ('1999-10-01','2000-01-10'), ('1997-01-01','1998-10-01');
select a,min(b) c,count(distinct rand()) from t1 group by a having c<a + interval 1 day;
a	c	count(distinct rand())
drop table t1;
CREATE TABLE t1 (a char(1));
INSERT INTO t1 VALUES ('A'),('B'),('A'),('B'),('A'),('B'),(NULL),('a'),('b'),(NULL),('A'),('B'),(NULL);
SELECT a FROM t1 GROUP BY a;
a
NULL
A
B
SELECT a,count(*) FROM t1 GROUP BY a;
a	count(*)
NULL	3
A	5
B	5
SELECT a FROM t1 GROUP BY binary a;
a
NULL
A
B
a
b
SELECT a,count(*) FROM t1 GROUP BY binary a;
a	count(*)
NULL	3
A	4
B	4
a	1
b	1
SELECT binary a FROM t1 GROUP BY 1;
binary a
NULL
A
B
a
b
SELECT binary a,count(*) FROM t1 GROUP BY 1;
binary a	count(*)
NULL	3
A	4
B	4
a	1
b	1
SET SQL_BIG_TABLES=1;
SELECT a FROM t1 GROUP BY a;
a
NULL
A
B
SELECT a,count(*) FROM t1 GROUP BY a;
a	count(*)
NULL	3
A	5
B	5
SELECT a FROM t1 GROUP BY binary a;
a
NULL
A
B
a
b
SELECT a,count(*) FROM t1 GROUP BY binary a;
a	count(*)
NULL	3
A	4
B	4
a	1
b	1
SELECT binary a FROM t1 GROUP BY 1;
binary a
NULL
A
B
a
b
SELECT binary a,count(*) FROM t1 GROUP BY 1;
binary a	count(*)
NULL	3
A	4
B	4
a	1
b	1
SET SQL_BIG_TABLES=0;
drop table t1;
CREATE TABLE t1 (
`a` char(193) default NULL,
`b` char(63) default NULL
);
INSERT INTO t1 VALUES ('abc','def'),('hij','klm');
SELECT CONCAT(a, b) FROM t1 GROUP BY 1;
CONCAT(a, b)
abcdef
hijklm
SELECT CONCAT(a, b),count(*) FROM t1 GROUP BY 1;
CONCAT(a, b)	count(*)
abcdef	1
hijklm	1
SELECT CONCAT(a, b),count(distinct a) FROM t1 GROUP BY 1;
CONCAT(a, b)	count(distinct a)
abcdef	1
hijklm	1
SELECT 1 FROM t1 GROUP BY CONCAT(a, b);
1
1
1
INSERT INTO t1 values ('hij','klm');
SELECT CONCAT(a, b),count(*) FROM t1 GROUP BY 1;
CONCAT(a, b)	count(*)
abcdef	1
hijklm	2
DROP TABLE t1;
create table t1 (One int unsigned, Two int unsigned, Three int unsigned, Four int unsigned);
insert into t1 values (1,2,1,4),(1,2,2,4),(1,2,3,4),(1,2,4,4),(1,1,1,4),(1,1,2,4),(1,1,3,4),(1,1,4,4),(1,3,1,4),(1,3,2,4),(1,3,3,4),(1,3,4,4);
select One, Two, sum(Four) from t1 group by One,Two;
One	Two	sum(Four)
1	1	16
1	2	16
1	3	16
drop table t1;
create table t1 (id integer primary key not null auto_increment, gender char(1));
insert into t1 values (NULL, 'M'), (NULL, 'F'),(NULL, 'F'),(NULL, 'F'),(NULL, 'M');
create table t2 (user_id integer not null, date date);
insert into t2 values (1, '2002-06-09'),(2, '2002-06-09'),(1, '2002-06-09'),(3, '2002-06-09'),(4, '2002-06-09'),(4, '2002-06-09');
select u.gender as gender, count(distinct  u.id) as dist_count, (count(distinct u.id)/5*100) as percentage from t1 u, t2 l where l.user_id = u.id group by u.gender;
gender	dist_count	percentage
F	3	60.0000
M	1	20.0000
select u.gender as  gender, count(distinct  u.id) as dist_count, (count(distinct u.id)/5*100) as percentage from t1 u, t2 l where l.user_id = u.id group by u.gender  order by percentage;
gender	dist_count	percentage
M	1	20.0000
F	3	60.0000
drop table t1,t2;
CREATE TABLE t1 (ID1 int, ID2 int, ID int NOT NULL AUTO_INCREMENT,PRIMARY KEY(ID
));
insert into t1 values (1,244,NULL),(2,243,NULL),(134,223,NULL),(185,186,NULL);
select S.ID as xID, S.ID1 as xID1 from t1 as S left join t1 as yS  on S.ID1 between yS.ID1 and yS.ID2;
xID	xID1
1	1
2	2
2	2
3	134
3	134
3	134
4	185
4	185
4	185
4	185
select S.ID as xID, S.ID1 as xID1, repeat('*',count(distinct yS.ID)) as Level from t1 as S left join t1 as yS  on S.ID1 between yS.ID1 and yS.ID2 group by xID order by xID1;
xID	xID1	Level
1	1	*
2	2	**
3	134	***
4	185	****
drop table t1;
CREATE TABLE t1 (
pid int(11) unsigned NOT NULL default '0',
c1id int(11) unsigned default NULL,
c2id int(11) unsigned default NULL,
value int(11) unsigned NOT NULL default '0',
UNIQUE KEY pid2 (pid,c1id,c2id),
UNIQUE KEY pid (pid,value)
) ENGINE=MyISAM;
INSERT INTO t1 VALUES (1, 1, NULL, 1),(1, 2, NULL, 2),(1, NULL, 3, 3),(1, 4, NULL, 4),(1, 5, NULL, 5);
CREATE TABLE t2 (
id int(11) unsigned NOT NULL default '0',
active enum('Yes','No') NOT NULL default 'Yes',
PRIMARY KEY  (id)
) ENGINE=MyISAM;
INSERT INTO t2 VALUES (1, 'Yes'),(2, 'No'),(4, 'Yes'),(5, 'No');
CREATE TABLE t3 (
id int(11) unsigned NOT NULL default '0',
active enum('Yes','No') NOT NULL default 'Yes',
PRIMARY KEY  (id)
);
INSERT INTO t3 VALUES (3, 'Yes');
select * from t1 AS m LEFT JOIN t2 AS c1 ON m.c1id = 
c1.id AND c1.active = 'Yes' LEFT JOIN t3 AS c2 ON m.c2id = c2.id AND 
c2.active = 'Yes' WHERE m.pid=1  AND (c1.id IS NOT NULL OR c2.id IS NOT NULL);
pid	c1id	c2id	value	id	active	id	active
1	1	NULL	1	1	Yes	NULL	NULL
1	NULL	3	3	NULL	NULL	3	Yes
1	4	NULL	4	4	Yes	NULL	NULL
select max(value) from t1 AS m LEFT JOIN t2 AS c1 ON 
m.c1id = c1.id AND c1.active = 'Yes' LEFT JOIN t3 AS c2 ON m.c2id = 
c2.id AND c2.active = 'Yes' WHERE m.pid=1  AND (c1.id IS NOT NULL OR c2.id IS 
NOT NULL);
max(value)
4
drop table t1,t2,t3;
create table t1 (a blob null);
insert into t1 values (NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(""),(""),(""),("b");
select a,count(*) from t1 group by a;
a	count(*)
NULL	9
	3
b	1
set option sql_big_tables=1;
select a,count(*) from t1 group by a;
a	count(*)
NULL	9
	3
b	1
drop table t1;
create table t1 (a int not null, b int not null);
insert into t1 values (1,1),(1,2),(3,1),(3,2),(2,2),(2,1);
create table t2 (a int not null, b int not null, key(a));
insert into t2 values (1,3),(3,1),(2,2),(1,1);
select t1.a,t2.b from t1,t2 where t1.a=t2.a group by t1.a,t2.b;
a	b
1	1
1	3
2	2
3	1
select t1.a,t2.b from t1,t2 where t1.a=t2.a group by t1.a,t2.b ORDER BY NULL;
a	b
1	3
3	1
2	2
1	1
explain select t1.a,t2.b from t1,t2 where t1.a=t2.a group by t1.a,t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	6	Using temporary; Using filesort
1	SIMPLE	t2	ALL	a	NULL	NULL	NULL	4	Using where; Using join buffer (flat, BNL join)
explain select t1.a,t2.b from t1,t2 where t1.a=t2.a group by t1.a,t2.b ORDER BY NULL;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	6	Using temporary
1	SIMPLE	t2	ALL	a	NULL	NULL	NULL	4	Using where; Using join buffer (flat, BNL join)
drop table t1,t2;
create table t1 (a int, b int);
insert into t1 values (1, 4),(10, 40),(1, 4),(10, 43),(1, 4),(10, 41),(1, 4),(10, 43),(1, 4);
select a, MAX(b), INTERVAL (MAX(b), 1,3,10,30,39,40,50,60,100,1000) from t1 group by a;
a	MAX(b)	INTERVAL (MAX(b), 1,3,10,30,39,40,50,60,100,1000)
1	4	2
10	43	6
select a, MAX(b), CASE MAX(b) when 4 then 4 when 43 then 43 else 0 end from t1 group by a;
a	MAX(b)	CASE MAX(b) when 4 then 4 when 43 then 43 else 0 end
1	4	4
10	43	43
select a, MAX(b), FIELD(MAX(b), '43', '4', '5') from t1 group by a;
a	MAX(b)	FIELD(MAX(b), '43', '4', '5')
1	4	2
10	43	1
select a, MAX(b), CONCAT_WS(MAX(b), '43', '4', '5') from t1 group by a;
a	MAX(b)	CONCAT_WS(MAX(b), '43', '4', '5')
1	4	434445
10	43	43434435
select a, MAX(b), ELT(MAX(b), 'a', 'b', 'c', 'd', 'e', 'f') from t1 group by a;
a	MAX(b)	ELT(MAX(b), 'a', 'b', 'c', 'd', 'e', 'f')
1	4	d
10	43	NULL
select a, MAX(b), MAKE_SET(MAX(b), 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h') from t1 group by a;
a	MAX(b)	MAKE_SET(MAX(b), 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h')
1	4	c
10	43	a,b,d,f
drop table t1;
create table t1 (id int not null, qty int not null);
insert into t1 values (1,2),(1,3),(2,4),(2,5);
select id, sum(qty) as sqty, count(qty) as cqty from t1 group by id having sum(qty)>2 and cqty>1;
id	sqty	cqty
1	5	2
2	9	2
select id, sum(qty) as sqty from t1 group by id having sqty>2 and count(qty)>1;
id	sqty
1	5
2	9
select id, sum(qty) as sqty, count(qty) as cqty from t1 group by id having sqty>2 and cqty>1;
id	sqty	cqty
1	5	2
2	9	2
select id, sum(qty) as sqty, count(qty) as cqty from t1 group by id having sum(qty)>2 and count(qty)>1;
id	sqty	cqty
1	5	2
2	9	2
select count(*), case interval(qty,2,3,4,5,6,7,8) when -1 then NULL when 0 then "zero" when 1 then "one" when 2 then "two" end as category from t1 group by category;
count(*)	category
2	NULL
1	one
1	two
select count(*), interval(qty,2,3,4,5,6,7,8) as category from t1 group by category;
count(*)	category
1	1
1	2
1	3
1	4
drop table t1;
CREATE TABLE t1 (
userid int(10) unsigned,
score smallint(5) unsigned,
key (score)
);
INSERT INTO t1 VALUES (1,1),(2,2),(1,1),(3,3),(3,3),(3,3),(3,3),(3,3);
SELECT userid,count(*) FROM t1 GROUP BY userid DESC;
userid	count(*)
3	5
2	1
1	2
EXPLAIN SELECT userid,count(*) FROM t1 GROUP BY userid DESC;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	8	Using temporary; Using filesort
DROP TABLE t1;
CREATE TABLE t1 (
i int(11) default NULL,
j int(11) default NULL
);
INSERT INTO t1 VALUES (1,2),(2,3),(4,5),(3,5),(1,5),(23,5);
SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL;
i	COUNT(DISTINCT(i))
1	1
2	1
4	4
explain SELECT i, COUNT(DISTINCT(i)) FROM t1 GROUP BY j ORDER BY NULL;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	6	Using filesort
DROP TABLE t1;
create table t1 (a int);
insert into t1 values(null);
select min(a) is null from t1;
min(a) is null
1
select min(a) is null or null from t1;
min(a) is null or null
1
select 1 and min(a) is null from t1;
1 and min(a) is null
1
drop table t1;
create table t1 ( col1 int, col2 int );
insert into t1 values (1,1),(1,2),(1,3),(2,1),(2,2);
select group_concat( distinct col1 ) as alias from t1
group by col2 having alias like '%';
alias
1,2
1,2
1
drop table t1;
create table t1 (a integer, b integer, c integer);
insert into t1 (a,b) values (1,2),(1,3),(2,5);
select a, 0.1*0+1 r2, sum(1) r1 from t1 where a = 1 group  by a having r1>1 and r2=1;
a	r2	r1
1	1.0	2
select a, round(rand(100)*10) r2, sum(1) r1 from t1 where a = 1 group  by a having r1>1 and r2<=2;
a	r2	r1
1	2	2
select a,sum(b) from t1 where a=1 group by c;
a	sum(b)
1	5
select a*sum(b) from t1 where a=1 group by c;
a*sum(b)
5
select sum(a)*sum(b) from t1 where a=1 group by c;
sum(a)*sum(b)
10
select a,sum(b) from t1 where a=1 group by c having a=1;
a	sum(b)
1	5
select a as d,sum(b) from t1 where a=1 group by c having d=1;
d	sum(b)
1	5
select sum(a)*sum(b) as d from t1 where a=1 group by c having d > 0;
d
10
drop table t1;
create table t1(a int);
insert into t1 values (0),(1),(2),(3),(4),(5),(6),(8),(9);
create table t2 (
a int,
b varchar(200) NOT NULL,
c varchar(50) NOT NULL,
d varchar(100) NOT NULL,
primary key (a,b(132),c,d),
key a (a,b)
) charset=utf8;
insert into t2 select 
x3.a,  -- 3
concat('val-', x3.a + 3*x4.a), -- 12
concat('val-', @a:=x3.a + 3*x4.a + 12*C.a), -- 120
concat('val-', @a + 120*D.a)
from t1 x3, t1 x4, t1 C, t1 D where x3.a < 3 and x4.a < 4 and D.a < 4;
delete from t2  where a = 2 and b = 'val-2' order by a,b,c,d limit 30;
explain select c from t2 where a = 2 and b = 'val-2' group by c;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	ref	PRIMARY,a	PRIMARY	402	const,const	#	Using where
select c from t2 where a = 2 and b = 'val-2' group by c;
c
val-74
val-98
drop table t1,t2;
create table t1 (b int4 unsigned not null);
insert into t1 values(3000000000);
select * from t1;
b
3000000000
select min(b) from t1;
min(b)
3000000000
drop table t1;
CREATE TABLE t1 (id int PRIMARY KEY, user_id int, hostname longtext);
INSERT INTO t1 VALUES
(1, 7, 'cache-dtc-af05.proxy.aol.com'),
(2, 3, 'what.ever.com'),
(3, 7, 'cache-dtc-af05.proxy.aol.com'),
(4, 7, 'cache-dtc-af05.proxy.aol.com');
SELECT hostname, COUNT(DISTINCT user_id) as no FROM t1
WHERE hostname LIKE '%aol%'
    GROUP BY hostname;
hostname	no
cache-dtc-af05.proxy.aol.com	1
DROP TABLE t1;
CREATE TABLE t1 (a  int, b int);
INSERT INTO t1 VALUES (1,2), (1,3);
SELECT a, b FROM t1 GROUP BY 'const';
a	b
1	2
SELECT DISTINCT a, b FROM t1 GROUP BY 'const';
a	b
1	2
DROP TABLE t1;
CREATE TABLE t1 (id INT, dt DATETIME);
INSERT INTO t1 VALUES ( 1, '2005-05-01 12:30:00' );
INSERT INTO t1 VALUES ( 1, '2005-05-01 12:30:00' );
INSERT INTO t1 VALUES ( 1, '2005-05-01 12:30:00' );
INSERT INTO t1 VALUES ( 1, '2005-05-01 12:30:00' );
SELECT dt DIV 1 AS f, id FROM t1 GROUP BY f;
f	id
20050501123000	1
DROP TABLE t1;
CREATE TABLE t1 (id varchar(20) NOT NULL);
INSERT INTO t1 VALUES ('trans1'), ('trans2');
CREATE TABLE t2 (id varchar(20) NOT NULL, err_comment blob NOT NULL);
INSERT INTO t2 VALUES ('trans1', 'a problem');
SELECT COUNT(DISTINCT(t1.id)), LEFT(err_comment, 256) AS comment
FROM t1 LEFT JOIN t2 ON t1.id=t2.id GROUP BY comment;
COUNT(DISTINCT(t1.id))	comment
1	NULL
1	a problem
DROP TABLE t1, t2;
create table t1 (f1 date);
insert into t1 values('2005-06-06');
insert into t1 values('2005-06-06');
select date(left(f1+0,8)) from t1 group by 1;
date(left(f1+0,8))
2005-06-06
drop table t1;
CREATE TABLE t1 (n int);
INSERT INTO t1 VALUES (1);
SELECT n+1 AS n FROM t1 GROUP BY n;
n
2
Warnings:
Warning	1052	Column 'n' in group statement is ambiguous
DROP TABLE t1;
create table t1(f1 varchar(5) key);
insert into t1 values (1),(2);
select sql_buffer_result max(f1) is null from t1;
max(f1) is null
0
select sql_buffer_result max(f1)+1 from t1;
max(f1)+1
3
drop table t1;
CREATE TABLE t1(a INT);
INSERT INTO t1 VALUES (1),(2);
SELECT a FROM t1 GROUP BY 'a';
a
1
SELECT a FROM t1 GROUP BY "a";
a
1
SELECT a FROM t1 GROUP BY `a`;
a
1
2
set sql_mode=ANSI_QUOTES;
SELECT a FROM t1 GROUP BY "a";
a
1
2
SELECT a FROM t1 GROUP BY 'a';
a
1
SELECT a FROM t1 GROUP BY `a`;
a
1
2
set sql_mode='';
SELECT a FROM t1 HAVING 'a' > 1;
a
Warnings:
Warning	1292	Truncated incorrect DOUBLE value: 'a'
SELECT a FROM t1 HAVING "a" > 1;
a
Warnings:
Warning	1292	Truncated incorrect DOUBLE value: 'a'
SELECT a FROM t1 HAVING `a` > 1;
a
2
SELECT a FROM t1 ORDER BY 'a' DESC;
a
1
2
SELECT a FROM t1 ORDER BY "a" DESC;
a
1
2
SELECT a FROM t1 ORDER BY `a` DESC;
a
2
1
DROP TABLE t1;
create table t1 (c1 char(3), c2 char(3));
create table t2 (c3 char(3), c4 char(3));
insert into t1 values ('aaa', 'bb1'), ('aaa', 'bb2');
insert into t2 values ('aaa', 'bb1'), ('aaa', 'bb2');
select t1.c1 as c2 from t1, t2 where t1.c2 = t2.c4
group by c2;
c2
aaa
aaa
Warnings:
Warning	1052	Column 'c2' in group statement is ambiguous
show warnings;
Level	Code	Message
Warning	1052	Column 'c2' in group statement is ambiguous
select t1.c1 as c2 from t1, t2 where t1.c2 = t2.c4
group by t1.c1;
c2
aaa
show warnings;
Level	Code	Message
drop table t1, t2;
CREATE TABLE t1 (a tinyint(3), b varchar(255), PRIMARY KEY  (a));
INSERT INTO t1 VALUES (1,'-----'), (6,'Allemagne'), (17,'Autriche'), 
(25,'Belgique'), (54,'Danemark'), (62,'Espagne'), (68,'France');
CREATE TABLE t2 (a tinyint(3), b tinyint(3), PRIMARY KEY  (a), KEY b (b));
INSERT INTO t2 VALUES (1,1), (2,1), (6,6), (18,17), (15,25), (16,25),
(17,25), (10,54), (5,62),(3,68);
CREATE VIEW v1 AS select t1.a, concat(t1.b,'') AS b, t1.b as real_b from t1;
explain 
SELECT straight_join sql_no_cache v1.a, v1.b, v1.real_b from t2, v1
where t2.b=v1.a GROUP BY t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	index	b	b	2	NULL	10	Using where; Using index
1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	1	test.t2.b	1	
SELECT straight_join sql_no_cache v1.a, v1.b, v1.real_b from t2, v1
where t2.b=v1.a GROUP BY t2.b;
a	b	real_b
1	-----	-----
6	Allemagne	Allemagne
17	Autriche	Autriche
25	Belgique	Belgique
54	Danemark	Danemark
62	Espagne	Espagne
68	France	France
DROP VIEW v1;
DROP TABLE t1,t2;
CREATE TABLE t1 (a INT PRIMARY KEY, b INT, key (b));
INSERT INTO t1 VALUES (1,      1);
INSERT INTO t1 SELECT  a + 1 , MOD(a + 1 , 20) FROM t1;
INSERT INTO t1 SELECT  a + 2 , MOD(a + 2 , 20) FROM t1;
INSERT INTO t1 SELECT  a + 4 , MOD(a + 4 , 20) FROM t1;
INSERT INTO t1 SELECT  a + 8 , MOD(a + 8 , 20) FROM t1;
INSERT INTO t1 SELECT  a + 16, MOD(a + 16, 20) FROM t1;
INSERT INTO t1 SELECT  a + 32, MOD(a + 32, 20) FROM t1;
INSERT INTO t1 SELECT  a + 64, MOD(a + 64, 20) FROM t1;
SELECT MIN(b), MAX(b) from t1;
MIN(b)	MAX(b)
0	19
EXPLAIN SELECT b, sum(1) FROM t1 GROUP BY b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	b	5	NULL	128	Using index
EXPLAIN SELECT SQL_BIG_RESULT b, sum(1) FROM t1 GROUP BY b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	b	5	NULL	128	Using index; Using filesort
SELECT b, sum(1) FROM t1 GROUP BY b;
b	sum(1)
0	6
1	7
2	7
3	7
4	7
5	7
6	7
7	7
8	7
9	6
10	6
11	6
12	6
13	6
14	6
15	6
16	6
17	6
18	6
19	6
SELECT SQL_BIG_RESULT b, sum(1) FROM t1 GROUP BY b;
b	sum(1)
0	6
1	7
2	7
3	7
4	7
5	7
6	7
7	7
8	7
9	6
10	6
11	6
12	6
13	6
14	6
15	6
16	6
17	6
18	6
19	6
DROP TABLE t1;
CREATE TABLE t1 (a INT, b INT,
PRIMARY KEY (a),
KEY i2(a,b));
INSERT INTO t1 VALUES (1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(7,7),(8,8);
INSERT INTO t1 SELECT a + 8,b FROM t1;
INSERT INTO t1 SELECT a + 16,b FROM t1;
INSERT INTO t1 SELECT a + 32,b FROM t1;
INSERT INTO t1 SELECT a + 64,b FROM t1;
INSERT INTO t1 SELECT a + 128,b FROM t1 limit 16;
ANALYZE TABLE t1;
Table	Op	Msg_type	Msg_text
test.t1	analyze	status	OK
EXPLAIN SELECT a FROM t1 WHERE a < 2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	PRIMARY,i2	PRIMARY	4	NULL	1	Using where; Using index
EXPLAIN SELECT a FROM t1 WHERE a < 2 ORDER BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	PRIMARY,i2	PRIMARY	4	NULL	1	Using where; Using index
EXPLAIN SELECT a FROM t1 WHERE a < 2 GROUP BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	PRIMARY,i2	PRIMARY	4	NULL	1	Using where; Using index for group-by
EXPLAIN SELECT a FROM t1 IGNORE INDEX (PRIMARY,i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	144	
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR JOIN (PRIMARY,i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	144	
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR GROUP BY (PRIMARY,i2) GROUP BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	PRIMARY	4	NULL	144	Using index
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	PRIMARY	4	NULL	144	Using index
SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY,i2) ORDER BY a;
a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
EXPLAIN SELECT a FROM t1 IGNORE INDEX FOR ORDER BY (PRIMARY)
IGNORE INDEX FOR GROUP BY (i2) GROUP BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	PRIMARY	4	NULL	144	Using index
EXPLAIN SELECT a FROM t1 IGNORE INDEX (PRIMARY) IGNORE INDEX FOR ORDER BY (i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	i2	9	NULL	144	Using index
EXPLAIN SELECT a FROM t1 FORCE INDEX (i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	i2	9	NULL	144	Using index
EXPLAIN SELECT a FROM t1 USE INDEX ();
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	144	
EXPLAIN SELECT a FROM t1 USE INDEX () USE INDEX (i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	144	
EXPLAIN SELECT a FROM t1 
FORCE INDEX (PRIMARY) 
IGNORE INDEX FOR GROUP BY (i2)
IGNORE INDEX FOR ORDER BY (i2)
USE INDEX (i2);
ERROR HY000: Incorrect usage of USE INDEX and FORCE INDEX
EXPLAIN SELECT a FROM t1 USE INDEX (i2) USE INDEX ();
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	i2	9	NULL	144	Using index
EXPLAIN SELECT a FROM t1 FORCE INDEX ();
ERROR 42000: 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 ')' at line 1
EXPLAIN SELECT a FROM t1 IGNORE INDEX ();
ERROR 42000: 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 ')' at line 1
EXPLAIN SELECT a FROM t1 USE INDEX FOR JOIN (i2) 
USE INDEX FOR GROUP BY (i2) GROUP BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	#	NULL	i2	#	NULL	#	#
EXPLAIN SELECT a FROM t1 FORCE INDEX FOR JOIN (i2) 
FORCE INDEX FOR GROUP BY (i2) GROUP BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	NULL	i2	4	NULL	145	Using index for group-by
EXPLAIN SELECT a FROM t1 USE INDEX () IGNORE INDEX (i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	144	
EXPLAIN SELECT a FROM t1 IGNORE INDEX (i2) USE INDEX ();
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	144	
EXPLAIN SELECT a FROM t1 
USE INDEX FOR GROUP BY (i2) 
USE INDEX FOR ORDER BY (i2)
USE INDEX FOR JOIN (i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	i2	9	NULL	144	Using index
EXPLAIN SELECT a FROM t1 
USE INDEX FOR JOIN (i2) 
USE INDEX FOR JOIN (i2) 
USE INDEX FOR JOIN (i2,i2);
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index	NULL	i2	9	NULL	144	Using index
EXPLAIN SELECT 1 FROM t1 WHERE a IN
(SELECT a FROM t1 USE INDEX (i2) IGNORE INDEX (i2));
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	index	PRIMARY,i2	PRIMARY	4	NULL	144	Using index
1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	144	Using where; FirstMatch(t1)
CREATE TABLE t2 (a INT, b INT, KEY(a));
INSERT INTO t2 VALUES (1, 1), (2, 2), (3,3), (4,4);
EXPLAIN SELECT a, SUM(b) FROM t2 GROUP BY a LIMIT 2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	index	NULL	a	5	NULL	2	
EXPLAIN SELECT a, SUM(b) FROM t2 IGNORE INDEX (a) GROUP BY a LIMIT 2;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	4	Using temporary; Using filesort
EXPLAIN SELECT 1 FROM t2 WHERE a IN
(SELECT a FROM t1 USE INDEX (i2) IGNORE INDEX (i2));
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t2	index	a	a	5	NULL	4	Using index
1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	144	Using where; FirstMatch(t2)
SHOW VARIABLES LIKE 'old';
Variable_name	Value
old	OFF
SET @@old = off;
ERROR HY000: Variable 'old' is a read only variable
DROP TABLE t1, t2;