drop table if exists t1;
create table t1 (id int not null, str char(10), unique(str));
explain select * from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	0	const row not found
insert into t1 values (1, null),(2, null),(3, "foo"),(4, "bar");
select * from t1 where str is null;
id	str
1	NULL
2	NULL
select * from t1 where str="foo";
id	str
3	foo
explain select * from t1 where str is null;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ref	str	str	11	const	1	Using where
explain select * from t1 where str="foo";
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	const	str	str	11	const	1	
explain select * from t1 ignore key (str) where str="foo";
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
explain select * from t1 use key (str,str) where str="foo";
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	const	str	str	11	const	1	
explain select * from t1 use key (str,str,foo) where str="foo";
ERROR 42000: Index 'foo' is not defined for table 't1'
explain select * from t1 ignore key (str,str,foo) where str="foo";
ERROR 42000: Index 'foo' is not defined for table 't1'
drop table t1;
explain select 1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
create table t1 (a int not null);
explain select count(*) from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
insert into t1 values(1);
explain select count(*) from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
insert into t1 values(1);
explain select count(*) from t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
drop table t1;
set names koi8r;
create table ��� (���0 int, ���1 int, key ���0 (���0), key ���01 (���0,���1));
insert into ��� (���0) values (1);
insert into ��� (���0) values (2);
explain select ���0 from ��� where ���0=1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	���	ref	���0,���01	���0	5	const	1	Using where; Using index
drop table ���;
set names latin1;