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drop table if exists t1,t2,t3;
CREATE TABLE t1 (a int not null, b char (10) not null);
insert into t1 values(1,'a'),(2,'b'),(3,'c'),(3,'c');
CREATE TABLE t2 (a int not null, b char (10) not null);
insert into t2 values (3,'c'),(4,'d'),(5,'f'),(6,'e');
select a,b from t1 union select a,b from t2;
a b
1 a
2 b
3 c
4 d
5 f
6 e
select a,b from t1 union all select a,b from t2;
a b
1 a
2 b
3 c
3 c
3 c
4 d
5 f
6 e
select a,b from t1 union all select a,b from t2 order by b;
a b
1 a
2 b
3 c
3 c
3 c
4 d
6 e
5 f
select a,b from t1 union all select a,b from t2 union select 7,'g';
a b
1 a
2 b
3 c
3 c
3 c
4 d
5 f
6 e
7 g
select 0,'#' union select a,b from t1 union all select a,b from t2 union select 7,'gg';
0 #
0 #
1 a
2 b
3 c
3 c
3 c
4 d
5 f
6 e
7 g
select a,b from t1 union select a,b from t1;
a b
1 a
2 b
3 c
select 't1',b,count(*) from t1 group by b UNION select 't2',b,count(*) from t2 group by b;
t1 b count(*)
t1 a 1
t1 b 1
t1 c 2
t2 c 1
t2 d 1
t2 e 1
t2 f 1
(select a,b from t1 limit 2) union all (select a,b from t2 order by a) limit 4;
a b
1 a
2 b
3 c
4 d
(select a,b from t1 limit 2) union all (select a,b from t2 order by a limit 1);
a b
1 a
2 b
3 c
(select a,b from t1 limit 2) union all (select a,b from t2 order by a limit 1) order by b desc;
a b
3 c
2 b
1 a
(select a,b from t1 limit 2) union all (select a,b from t2 order by a limit 1) order by t1.b;
Table 't1' from one of SELECT's can not be used in order clause
explain (select a,b from t1 limit 2) union all (select a,b from t2 order by a limit 1) order by b desc;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4
2 UNION t2 ALL NULL NULL NULL NULL 4 Using filesort
select found_rows();
FOUND_ROWS()
0
explain select a,b from t1 union all select a,b from t2;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4
2 UNION t2 ALL NULL NULL NULL NULL 4
explain select xx from t1 union select 1;
Unknown column 'xx' in 'field list'
explain select a,b from t1 union select 1;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 4
2 UNION NULL NULL NULL NULL NULL NULL NULL No tables used
explain select 1 union select a,b from t1 union select 1;
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 UNION t1 ALL NULL NULL NULL NULL 4
3 UNION NULL NULL NULL NULL NULL NULL NULL No tables used
explain select a,b from t1 union select 1 limit 0;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
2 UNION NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
select a,b from t1 into outfile 'skr' union select a,b from t2;
Wrong usage of UNION and INTO
select a,b from t1 order by a union select a,b from t2;
Wrong usage of UNION and ORDER BY
insert into t3 select a from t1 order by a union select a from t2;
Wrong usage of UNION and ORDER BY
create table t3 select a,b from t1 union select a from t2;
The used SELECT statements have a different number of columns
select a,b from t1 union select a from t2;
The used SELECT statements have a different number of columns
select * from t1 union select a from t2;
The used SELECT statements have a different number of columns
select a from t1 union select * from t2;
The used SELECT statements have a different number of columns
select * from t1 union select SQL_BUFFER_RESULT * from t2;
Wrong usage/placement of 'SQL_BUFFER_RESULT'
create table t3 select a,b from t1 union all select a,b from t2;
insert into t3 select a,b from t1 union all select a,b from t2;
replace into t3 select a,b as c from t1 union all select a,b from t2;
drop table t1,t2,t3;
CREATE TABLE t1 (
`pseudo` char(35) NOT NULL default '',
`pseudo1` char(35) NOT NULL default '',
`same` tinyint(1) unsigned NOT NULL default '1',
PRIMARY KEY (`pseudo1`),
KEY `pseudo` (`pseudo`)
) TYPE=MyISAM;
INSERT INTO t1 (pseudo,pseudo1,same) VALUES ('joce', 'testtt', 1),('joce', 'tsestset', 1),('dekad', 'joce', 1);
SELECT pseudo FROM t1 WHERE pseudo1='joce' UNION SELECT pseudo FROM t1 WHERE pseudo='joce';
pseudo
dekad
joce
SELECT pseudo1 FROM t1 WHERE pseudo1='joce' UNION SELECT pseudo1 FROM t1 WHERE pseudo='joce';
pseudo1
joce
testtt
tsestset
SELECT * FROM t1 WHERE pseudo1='joce' UNION SELECT * FROM t1 WHERE pseudo='joce' order by pseudo desc,pseudo1 desc;
pseudo pseudo1 same
joce tsestset 1
joce testtt 1
dekad joce 1
SELECT pseudo1 FROM t1 WHERE pseudo='joce' UNION SELECT pseudo FROM t1 WHERE pseudo1='joce';
pseudo1
testtt
tsestset
dekad
SELECT pseudo1 FROM t1 WHERE pseudo='joce' UNION ALL SELECT pseudo FROM t1 WHERE pseudo1='joce';
pseudo1
testtt
tsestset
dekad
SELECT pseudo1 FROM t1 WHERE pseudo='joce' UNION SELECT 1;
pseudo1
testtt
tsestset
1
drop table t1;
drop table if exists t1,t2;
create table t1 (a int);
create table t2 (a int);
insert into t1 values (1),(2),(3),(4),(5);
insert into t2 values (11),(12),(13),(14),(15);
(select * from t1 limit 2) union (select * from t2 limit 3) limit 4;
a
1
2
11
12
(select * from t1 limit 2) union (select * from t2 limit 3);
a
1
2
11
12
13
(select * from t1 limit 2) union (select * from t2 limit 20,3);
a
1
2
set SQL_SELECT_LIMIT=2;
(select * from t1 limit 1) union (select * from t2 limit 3);
a
1
11
set SQL_SELECT_LIMIT=DEFAULT;
drop table t1,t2;
select * union select 1;
No tables used
select 1 as a,(select a union select a);
a (select a union select a)
1 1
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