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drop table if exists t1;
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;
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