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
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
|
drop table if exists t1,t2,t3,t4,t5,t6;
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 global 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;
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;
CREATE TABLE t1 (
cid smallint(5) unsigned NOT NULL default '0',
cv varchar(250) NOT NULL default '',
PRIMARY KEY (cid),
UNIQUE KEY cv (cv)
) ;
INSERT INTO t1 VALUES (8,'dummy');
CREATE TABLE t2 (
cid bigint(20) unsigned NOT NULL auto_increment,
cap varchar(255) NOT NULL default '',
PRIMARY KEY (cid),
KEY cap (cap)
) ;
CREATE TABLE t3 (
gid bigint(20) unsigned NOT NULL auto_increment,
gn varchar(255) NOT NULL default '',
must tinyint(4) default NULL,
PRIMARY KEY (gid),
KEY gn (gn)
) ;
INSERT INTO t3 VALUES (1,'V1',NULL);
CREATE TABLE t4 (
uid bigint(20) unsigned NOT NULL default '0',
gid bigint(20) unsigned default NULL,
rid bigint(20) unsigned default NULL,
cid bigint(20) unsigned default NULL,
UNIQUE KEY m (uid,gid,rid,cid),
KEY uid (uid),
KEY rid (rid),
KEY cid (cid),
KEY container (gid,rid,cid)
) ;
INSERT INTO t4 VALUES (1,1,NULL,NULL);
CREATE TABLE t5 (
rid bigint(20) unsigned NOT NULL auto_increment,
rl varchar(255) NOT NULL default '',
PRIMARY KEY (rid),
KEY rl (rl)
) ;
CREATE TABLE t6 (
uid bigint(20) unsigned NOT NULL auto_increment,
un varchar(250) NOT NULL default '',
uc smallint(5) unsigned NOT NULL default '0',
PRIMARY KEY (uid),
UNIQUE KEY nc (un,uc),
KEY un (un)
) ;
INSERT INTO t6 VALUES (1,'test',8);
SELECT t4.uid, t5.rl, t3.gn as g1, t4.cid, t4.gid as gg FROM t3, t6, t1, t4 left join t5 on t5.rid = t4.rid left join t2 on t2.cid = t4.cid WHERE t3.gid=t4.gid AND t6.uid = t4.uid AND t6.uc = t1.cid AND t1.cv = "dummy" AND t6.un = "test";
uid rl g1 cid gg
1 NULL V1 NULL 1
SELECT t4.uid, t5.rl, t3.gn as g1, t4.cid, t4.gid as gg FROM t3, t6, t1, t4 left join t5 on t5.rid = t4.rid left join t2 on t2.cid = t4.cid WHERE t3.gid=t4.gid AND t6.uid = t4.uid AND t3.must IS NOT NULL AND t6.uc = t1.cid AND t1.cv = "dummy" AND t6.un = "test";
uid rl g1 cid gg
(SELECT t4.uid, t5.rl, t3.gn as g1, t4.cid, t4.gid as gg FROM t3, t6, t1, t4 left join t5 on t5.rid = t4.rid left join t2 on t2.cid = t4.cid WHERE t3.gid=t4.gid AND t6.uid = t4.uid AND t3.must IS NOT NULL AND t6.uc = t1.cid AND t1.cv = "dummy" AND t6.un = "test") UNION (SELECT t4.uid, t5.rl, t3.gn as g1, t4.cid, t4.gid as gg FROM t3, t6, t1, t4 left join t5 on t5.rid = t4.rid left join t2 on t2.cid = t4.cid WHERE t3.gid=t4.gid AND t6.uid = t4.uid AND t6.uc = t1.cid AND t1.cv = "dummy" AND t6.un = "test");
uid rl g1 cid gg
1 NULL V1 NULL 1
drop table t1,t2,t3,t4,t5,t6;
select * union select 1;
No tables used
select 1 as a,(select a union select a);
a (select a union select a)
1 1
CREATE TABLE t1 ( id int(3) unsigned default '0') TYPE=MyISAM;
INSERT INTO t1 (id) VALUES("1");
CREATE TABLE t2 ( id int(3) unsigned default '0', id_master int(5) default '0', text1 varchar(5) default NULL, text2 varchar(5) default NULL) TYPE=MyISAM;
INSERT INTO t2 (id, id_master, text1, text2) VALUES("1", "1",
"foo1", "bar1");
INSERT INTO t2 (id, id_master, text1, text2) VALUES("2", "1",
"foo2", "bar2");
INSERT INTO t2 (id, id_master, text1, text2) VALUES("3", "1", NULL,
"bar3");
INSERT INTO t2 (id, id_master, text1, text2) VALUES("4", "1",
"foo4", "bar4");
SELECT 1 AS id_master, 1 AS id, NULL AS text1, 'ABCDE' AS text2 UNION SELECT id_master, t2.id, text1, text2 FROM t1 LEFT JOIN t2 ON t1.id = t2.id_master;
id_master id text1 text2
1 1 NULL ABCDE
1 1 bar1
1 2 bar2
1 3 NULL bar3
1 4 bar4
SELECT 1 AS id_master, 1 AS id, 'ABCDE' AS text1, 'ABCDE' AS text2 UNION SELECT id_master, t2.id, text1, text2 FROM t1 LEFT JOIN t2 ON t1.id = t2.id_master;
id_master id text1 text2
1 1 ABCDE ABCDE
1 1 foo1 bar1
1 2 foo2 bar2
1 3 NULL bar3
1 4 foo4 bar4
drop table if exists t1,t2;
(SELECT 1,3) UNION (SELECT 2,1) ORDER BY (SELECT 2);
1 3
1 3
2 1
create table t1 (a int not null primary key auto_increment, b int, key(b));
create table t2 (a int not null primary key auto_increment, b int);
insert into t1 (b) values (1),(2),(2),(3);
insert into t2 (b) values (10),(11),(12),(13);
explain (select * from t1 where a=1) union (select * from t2 where a=1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 const PRIMARY PRIMARY 4 const 1
2 UNION t2 const PRIMARY PRIMARY 4 const 1
(select * from t1 where a=5) union (select * from t2 where a=1);
a b
1 10
(select * from t1 where a=5 and a=6) union (select * from t2 where a=1);
a b
1 10
(select t1.a,t1.b from t1,t2 where t1.a=5) union (select * from t2 where a=1);
a b
1 10
(select * from t1 where a=1) union (select t1.a,t2.a from t1,t2 where t1.a=t2.a);
a b
1 1
2 2
3 3
4 4
explain (select * from t1 where a=1 and b=10) union (select t1.a,t2.a from t1,t2 where t1.a=t2.a);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
2 UNION t1 index PRIMARY PRIMARY 4 NULL 4 Using index
2 UNION t2 index PRIMARY PRIMARY 4 NULL 4 Using where; Using index
explain (select * from t1 where a=1) union (select * from t1 where b=1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 const PRIMARY PRIMARY 4 const 1
2 UNION t1 ref b b 5 const 1 Using where
drop table t1,t2;
(select 1) union (select 2) order by 0;
Unknown column '0' in 'order clause'
SELECT @a:=1 UNION SELECT @a:=@a+1;
@a:=1
1
2
(SELECT 1) UNION (SELECT 2) ORDER BY (SELECT a);
Unknown column 'a' in 'field list'
|
