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
|
drop table if exists t1;
SET SQL_SAFE_UPDATES=1,SQL_SELECT_LIMIT=4, MAX_JOIN_SIZE=9;
create table t1 (a int auto_increment primary key, b char(20));
insert into t1 values(1,"test");
SELECT SQL_BUFFER_RESULT * from t1;
a b
1 test
update t1 set b="a" where a=1;
delete from t1 where a=1;
insert into t1 values(1,"test"),(2,"test2");
SELECT SQL_BUFFER_RESULT * from t1;
a b
1 test
2 test2
update t1 set b="a" where a=1;
select 1 from t1,t1 as t2,t1 as t3;
1
1
1
1
1
update t1 set b="a";
ERROR HY000: You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
update t1 set b="a" where b="test";
ERROR HY000: You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
delete from t1;
ERROR HY000: You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
delete from t1 where b="test";
ERROR HY000: You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
delete from t1 where a+0=1;
ERROR HY000: You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
select 1 from t1,t1 as t2,t1 as t3,t1 as t4,t1 as t5;
ERROR 42000: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
update t1 set b="a" limit 1;
update t1 set b="a" where b="b" limit 2;
delete from t1 where b="test" limit 1;
delete from t1 where a+0=1 limit 2;
alter table t1 add key b (b);
SET MAX_JOIN_SIZE=2;
SELECT @@MAX_JOIN_SIZE, @@SQL_BIG_SELECTS;
@@MAX_JOIN_SIZE @@SQL_BIG_SELECTS
2 0
insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
SELECT * from t1 order by a;
ERROR 42000: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
SET SQL_BIG_SELECTS=1;
SELECT * from t1 order by a;
a b
2 test2
3 a
4 a
5 a
SET MAX_JOIN_SIZE=2;
SELECT * from t1;
ERROR 42000: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
SET MAX_JOIN_SIZE=DEFAULT;
SELECT * from t1;
a b
2 test2
3 a
4 a
5 a
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status OK
insert into t1 values (null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a"),(null,"a");
explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL b NULL NULL NULL 21
1 SIMPLE t2 ref b b 21 test.t1.b 6 Using where
set MAX_SEEKS_FOR_KEY=1;
explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL b NULL NULL NULL 21
1 SIMPLE t2 ref b b 21 test.t1.b 6 Using where
SET MAX_SEEKS_FOR_KEY=DEFAULT;
drop table t1;
create table t1 (a int);
insert into t1 values (1),(2),(3),(4),(5);
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
set local max_join_size=8;
select * from (select * from t1) x;
ERROR 42000: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
set local max_join_size=1;
select * from (select a.a as aa, b.a as ba from t1 a, t1 b) x;
ERROR 42000: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
set local max_join_size=1;
select * from (select 1 union select 2 union select 3) x;
ERROR 42000: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
drop table t1;
SET SQL_SAFE_UPDATES=0,SQL_SELECT_LIMIT=DEFAULT, MAX_JOIN_SIZE=DEFAULT;
|
