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drop table if exists t1,t2;
create table t1
(
key1 int not null,
key2 int not null,
INDEX i1(key1),
INDEX i2(key2)
) engine=innodb;
explain select * from t1 where key1 < 5 or key2 > 197;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge i1,i2 i1,i2 4,4 NULL 8 Using sort_union(i1,i2); Using where
select * from t1 where key1 < 5 or key2 > 197;
key1 key2
0 200
1 199
2 198
3 197
4 196
explain select * from t1 where key1 < 3 or key2 > 195;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge i1,i2 i1,i2 4,4 NULL 8 Using sort_union(i1,i2); Using where
select * from t1 where key1 < 3 or key2 > 195;
key1 key2
0 200
1 199
2 198
3 197
4 196
alter table t1 add str1 char (255) not null,
add zeroval int not null default 0,
add str2 char (255) not null,
add str3 char (255) not null;
update t1 set str1='aaa', str2='bbb', str3=concat(key2, '-', key1 div 2, '_' ,if(key1 mod 2 = 0, 'a', 'A'));
alter table t1 add primary key (str1, zeroval, str2, str3);
explain select * from t1 where key1 < 5 or key2 > 197;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge i1,i2 i1,i2 4,4 NULL 8 Using sort_union(i1,i2); Using where
select * from t1 where key1 < 5 or key2 > 197;
key1 key2 str1 zeroval str2 str3
4 196 aaa 0 bbb 196-2_a
3 197 aaa 0 bbb 197-1_A
2 198 aaa 0 bbb 198-1_a
1 199 aaa 0 bbb 199-0_A
0 200 aaa 0 bbb 200-0_a
explain select * from t1 where key1 < 3 or key2 > 195;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge i1,i2 i1,i2 4,4 NULL 8 Using sort_union(i1,i2); Using where
select * from t1 where key1 < 3 or key2 > 195;
key1 key2 str1 zeroval str2 str3
4 196 aaa 0 bbb 196-2_a
3 197 aaa 0 bbb 197-1_A
2 198 aaa 0 bbb 198-1_a
1 199 aaa 0 bbb 199-0_A
0 200 aaa 0 bbb 200-0_a
drop table t1;
create table t1 (
pk integer not null auto_increment primary key,
key1 integer,
key2 integer not null,
filler char (200),
index (key1),
index (key2)
) engine=innodb;
show warnings;
Level Code Message
explain select pk from t1 where key1 = 1 and key2 = 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge key1,key2 key1,key2 5,4 NULL 1 Using intersect(key1,key2); Using where; Using index
select pk from t1 where key2 = 1 and key1 = 1;
pk
26
27
select pk from t1 ignore index(key1,key2) where key2 = 1 and key1 = 1;
pk
26
27
drop table t1;
create table t1 (
pk int primary key auto_increment,
key1a int,
key2a int,
key1b int,
key2b int,
dummy1 int,
dummy2 int,
dummy3 int,
dummy4 int,
key3a int,
key3b int,
filler1 char (200),
index i1(key1a, key1b),
index i2(key2a, key2b),
index i3(key3a, key3b)
) engine=innodb;
create table t2 (a int);
insert into t2 values (0),(1),(2),(3),(4),(NULL);
insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b)
select A.a, B.a, C.a, D.a, C.a, D.a from t2 A,t2 B,t2 C, t2 D;
insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b)
select key1a, key1b, key2a, key2b, key3a, key3b from t1;
insert into t1 (key1a, key1b, key2a, key2b, key3a, key3b)
select key1a, key1b, key2a, key2b, key3a, key3b from t1;
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status OK
select count(*) from t1;
count(*)
5184
explain select count(*) from t1 where
key1a = 2 and key1b is null and key2a = 2 and key2b is null;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge i1,i2 i1,i2 10,10 NULL 3 Using intersect(i1,i2); Using where; Using index
select count(*) from t1 where
key1a = 2 and key1b is null and key2a = 2 and key2b is null;
count(*)
4
explain select count(*) from t1 where
key1a = 2 and key1b is null and key3a = 2 and key3b is null;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index_merge i1,i3 i1,i3 10,10 NULL 3 Using intersect(i1,i3); Using where; Using index
select count(*) from t1 where
key1a = 2 and key1b is null and key3a = 2 and key3b is null;
count(*)
4
drop table t1,t2;
create table t1 (
id1 int,
id2 date ,
index idx2 (id1,id2),
index idx1 (id2)
) engine = innodb;
insert into t1 values(1,'20040101'), (2,'20040102');
select * from t1 where id1 = 1 and id2= '20040101';
id1 id2
1 2004-01-01
drop table t1;
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