SET SESSION DEFAULT_STORAGE_ENGINE = InnoDB;
drop table if exists t1, t2, t3,t4;
create table t1 (
pk1 int not NULL,
key1 int(11),
key2 int(11),
PRIMARY KEY  (pk1),
KEY key1 (key1),
KEY key2 (key2)
);
insert into t1 values (-5, 1, 1),
(-100, 1, 1),
(3, 1, 1),
(0, 1, 1),
(10, 1, 1);
explain select * from t1 force index(key1, key2) where key1 < 3 or key2 < 3;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	index_merge	key1,key2	key1,key2	5,5	NULL	5	Using sort_union(key1,key2); Using where
select * from t1 force index(key1, key2) where key1 < 3 or key2 < 3;
pk1	key1	key2
-100	1	1
-5	1	1
0	1	1
3	1	1
10	1	1
drop table t1;
create table t1 (
pk1 int unsigned not NULL,
key1 int(11),
key2 int(11),
PRIMARY KEY  (pk1),
KEY key1 (key1),
KEY key2 (key2)
);
insert into t1 values (0, 1, 1),
(0xFFFFFFFF, 1, 1),
(0xFFFFFFFE, 1, 1),
(1, 1, 1),
(2, 1, 1);
select * from t1 force index(key1, key2) where key1 < 3 or key2 < 3;
pk1	key1	key2
0	1	1
1	1	1
2	1	1
4294967294	1	1
4294967295	1	1
drop table t1;
create table t1 (
pk1 char(4) not NULL,
key1 int(11),
key2 int(11),
PRIMARY KEY  (pk1),
KEY key1 (key1),
KEY key2 (key2)
) collate latin2_general_ci;
insert into t1 values ('a1', 1, 1),
('b2', 1, 1),
('A3', 1, 1),
('B4', 1, 1);
select * from t1 force index(key1, key2) where key1 < 3 or key2 < 3;
pk1	key1	key2
a1	1	1
A3	1	1
b2	1	1
B4	1	1
drop table t1;
create table t1 (
pk1 int not NULL,
pk2 char(4) not NULL collate latin1_german1_ci,
pk3 char(4) not NULL collate latin1_bin,
key1 int(11),
key2 int(11),
PRIMARY KEY  (pk1,pk2,pk3),
KEY key1 (key1),
KEY key2 (key2)
);
insert into t1 values
(1, 'u', 'u',        1, 1),
(1, 'u', char(0xEC), 1, 1),
(1, 'u', 'x',        1, 1);
insert ignore into t1 select pk1, char(0xEC), pk3, key1, key2  from t1;
insert ignore into t1 select pk1, 'x', pk3, key1, key2  from t1 where pk2='u';
insert ignore into t1 select 2, pk2, pk3, key1, key2  from t1;
select * from t1;
pk1	pk2	pk3	key1	key2
1	ì	u	1	1
1	ì	x	1	1
1	ì	ì	1	1
1	u	u	1	1
1	u	x	1	1
1	u	ì	1	1
1	x	u	1	1
1	x	x	1	1
1	x	ì	1	1
2	ì	u	1	1
2	ì	x	1	1
2	ì	ì	1	1
2	u	u	1	1
2	u	x	1	1
2	u	ì	1	1
2	x	u	1	1
2	x	x	1	1
2	x	ì	1	1
select * from t1 force index(key1, key2) where key1 < 3 or key2 < 3;
pk1	pk2	pk3	key1	key2
1	ì	u	1	1
1	ì	x	1	1
1	ì	ì	1	1
1	u	u	1	1
1	u	x	1	1
1	u	ì	1	1
1	x	u	1	1
1	x	x	1	1
1	x	ì	1	1
2	ì	u	1	1
2	ì	x	1	1
2	ì	ì	1	1
2	u	u	1	1
2	u	x	1	1
2	u	ì	1	1
2	x	u	1	1
2	x	x	1	1
2	x	ì	1	1
alter table t1 drop primary key;
select * from t1;
pk1	pk2	pk3	key1	key2
1	ì	u	1	1
1	ì	x	1	1
1	ì	ì	1	1
1	u	u	1	1
1	u	x	1	1
1	u	ì	1	1
1	x	u	1	1
1	x	x	1	1
1	x	ì	1	1
2	ì	u	1	1
2	ì	x	1	1
2	ì	ì	1	1
2	u	u	1	1
2	u	x	1	1
2	u	ì	1	1
2	x	u	1	1
2	x	x	1	1
2	x	ì	1	1
select * from t1 force index(key1, key2) where key1 < 3 or key2 < 3;
pk1	pk2	pk3	key1	key2
1	ì	u	1	1
1	ì	x	1	1
1	ì	ì	1	1
1	u	u	1	1
1	u	x	1	1
1	u	ì	1	1
1	x	u	1	1
1	x	x	1	1
1	x	ì	1	1
2	ì	u	1	1
2	ì	x	1	1
2	ì	ì	1	1
2	u	u	1	1
2	u	x	1	1
2	u	ì	1	1
2	x	u	1	1
2	x	x	1	1
2	x	ì	1	1
drop table t1;
create table t1  (
pk1 varchar(8) NOT NULL default '',
pk2 varchar(4) NOT NULL default '',
key1 int(11),
key2 int(11),
primary key(pk1, pk2),
KEY key1 (key1),
KEY key2 (key2)
);
insert into t1 values ('','empt',2,2),
('a','a--a',2,2),
('bb','b--b',2,2),
('ccc','c--c',2,2),
('dddd','d--d',2,2);
select * from t1 force index(key1, key2) where key1 < 3 or key2 < 3;
pk1	pk2	key1	key2
	empt	2	2
a	a--a	2	2
bb	b--b	2	2
ccc	c--c	2	2
dddd	d--d	2	2
drop table t1;