explain.result 2.56 KB
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drop table if exists t1;
create table t1 (id int not null, str char(10), unique(str));
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explain select * from t1;
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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
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insert into t1 values (1, null),(2, null),(3, "foo"),(4, "bar");
select * from t1 where str is null;
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id	str
1	NULL
2	NULL
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select * from t1 where str="foo";
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id	str
3	foo
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explain select * from t1 where str is null;
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id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
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1	SIMPLE	t1	ref	str	str	11	const	1	Using where
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explain select * from t1 where str="foo";
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id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
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1	SIMPLE	t1	const	str	str	11	const	1	
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explain select * from t1 ignore key (str) where str="foo";
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id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
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1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using where
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explain select * from t1 use key (str,str) where str="foo";
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id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
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1	SIMPLE	t1	const	str	str	11	const	1	
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explain select * from t1 use key (str,str,foo) where str="foo";
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ERROR 42000: Key column 'foo' doesn't exist in table
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explain select * from t1 ignore key (str,str,foo) where str="foo";
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ERROR 42000: Key column 'foo' doesn't exist in table
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drop table t1;
explain select 1;
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id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
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1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
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create table t1 (a int not null);
explain select count(*) from t1;
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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
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insert into t1 values(1);
explain select count(*) from t1;
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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
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insert into t1 values(1);
explain select count(*) from t1;
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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
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drop table t1;
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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;
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select 3 into @v1;
explain select 3 into @v1;
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