mariadb/mysql-test/r/explain.result

drop table if exists t1;
create table t1 (id int not null, str char(10), unique(str));
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";
Key column 'foo' doesn't exist in table
explain select * from t1 ignore key (str,str,foo) where str="foo";
Key column 'foo' doesn't exist in table
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