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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: Key 'foo' doesn't exist in table 't1'
explain select * from t1 ignore key (str,str,foo) where str="foo";
ERROR 42000: Key 'foo' doesn't exist in 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 таб (кол0 int, кол1 int, key инд0 (кол0), key инд01 (кол0,кол1));
insert into таб (кол0) values (1);
insert into таб (кол0) values (2);
explain select кол0 from таб where кол0=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE таб ref инд0,инд01 инд0 5 const 1 Using where; Using index
drop table таб;
set names latin1;
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
create table t1(f1 int, f2 int);
insert into t1 values (1,1);
create view v1 as select * from t1 where f1=1;
explain extended select * from v1 where f2=1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1`,'1' AS `f2` from dual where 1
explain extended select * from t1 where 0;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
Warnings:
Note 1003 select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f2` AS `f2` from `test`.`t1` where 0
explain extended select * from t1 where 1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1`,'1' AS `f2` from dual where 1
explain extended select * from t1 having 0;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible HAVING
Warnings:
Note 1003 select `test`.`t1`.`f1` AS `f1`,`test`.`t1`.`f2` AS `f2` from `test`.`t1` having 0
explain extended select * from t1 having 1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1`,'1' AS `f2` from dual having 1
drop view v1;
drop table t1;
CREATE TABLE t1(c INT);
INSERT INTO t1 VALUES (),();
CREATE TABLE t2 (b INT,
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b),
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b),
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b),
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b),
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b),
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b),
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b),
KEY(b),KEY(b),KEY(b),KEY(b),KEY(b));
INSERT INTO t2 VALUES (),(),();
EXPLAIN SELECT 1 FROM
(SELECT 1 FROM t2,t1 WHERE b < c GROUP BY 1 LIMIT 1) AS d2;
id select_type table type possible_keys key key_len ref rows Extra
X X X X X X X X X const row not found
X X X X X X X X X
X X X X X X X X X Range checked for each record (index map: 0xFFFFFFFFFF)
DROP TABLE t2;
DROP TABLE t1;
CREATE TABLE t1(a INT);
CREATE TABLE t2(a INT);
INSERT INTO t1 VALUES (1),(2);
INSERT INTO t2 VALUES (1),(2);
EXPLAIN EXTENDED SELECT 1
FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00
2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer
Warnings:
Note 1003 select 1 AS `1` from (select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1`
EXPLAIN EXTENDED SELECT 1
FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00
2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer
Warnings:
Note 1003 select 1 AS `1` from (select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1`
prepare s1 from
'EXPLAIN EXTENDED SELECT 1
FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1';
execute s1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00
2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer
Warnings:
Note 1003 select 1 AS `1` from (select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1`
prepare s1 from
'EXPLAIN EXTENDED SELECT 1
FROM (SELECT COUNT(DISTINCT t1.a) FROM t1,t2 GROUP BY t1.a) AS s1';
execute s1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00
2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer
Warnings:
Note 1003 select 1 AS `1` from (select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1`
execute s1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 100.00
2 DERIVED t1 ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
2 DERIVED t2 ALL NULL NULL NULL NULL 2 100.00 Using join buffer
Warnings:
Note 1003 select 1 AS `1` from (select count(distinct `test`.`t1`.`a`) AS `COUNT(DISTINCT t1.a)` from `test`.`t1` join `test`.`t2` group by `test`.`t1`.`a`) `s1`
DROP TABLE t1,t2;
CREATE TABLE t1 (a INT PRIMARY KEY);
EXPLAIN EXTENDED SELECT COUNT(a) FROM t1 USE KEY(a);
ERROR 42000: Key 'a' doesn't exist in table 't1'
DROP TABLE t1;
CREATE TABLE t1(a LONGTEXT);
INSERT INTO t1 VALUES (repeat('a',@@global.max_allowed_packet));
INSERT INTO t1 VALUES (repeat('b',@@global.max_allowed_packet));
EXPLAIN SELECT DISTINCT 1 FROM t1,
(SELECT DISTINCTROW a AS away FROM t1 GROUP BY a WITH ROLLUP) as d1
WHERE t1.a = d1.a;
ERROR 42S22: Unknown column 'd1.a' in 'where clause'
DROP TABLE t1;
#
# Bug#37870: Usage of uninitialized value caused failed assertion.
#
create table t1 (dt datetime not null, t time not null);
create table t2 (dt datetime not null);
insert into t1 values ('2001-01-01 1:1:1', '1:1:1'),
('2001-01-01 1:1:1', '1:1:1');
insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');
flush tables;
EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY OUTR ALL NULL NULL NULL NULL 2 Using where
2 DEPENDENT SUBQUERY INNR ALL NULL NULL NULL NULL 2 Using where
flush tables;
SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
dt
flush tables;
EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' );
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY OUTR ALL NULL NULL NULL NULL 2 Using where
2 DEPENDENT SUBQUERY INNR ALL NULL NULL NULL NULL 2 Using where
flush tables;
SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' );
dt
2001-01-01 01:01:01
2001-01-01 01:01:01
drop tables t1, t2;
#
# Bug#48295:
# explain extended crash with subquery and ONLY_FULL_GROUP_BY sql_mode
#
CREATE TABLE t1 (f1 INT);
SELECT @@session.sql_mode INTO @old_sql_mode;
SET SESSION sql_mode='ONLY_FULL_GROUP_BY';
EXPLAIN EXTENDED SELECT 1 FROM t1
WHERE f1 > ALL( SELECT t.f1 FROM t1,t1 AS t );
ERROR 42000: Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause
SHOW WARNINGS;
Level Code Message
Error 1140 Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause
Note 1003 select 1 AS `1` from `test`.`t1` where <not>(<exists>(...))
SET SESSION sql_mode=@old_sql_mode;
DROP TABLE t1;
#
# Bug#30302: Tables that were optimized away are printed in the
# EXPLAIN EXTENDED warning.
#
create table t1(f1 int);
create table t2(f2 int);
insert into t1 values(1);
insert into t2 values(1),(2);
explain extended select * from t1 where f1=1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
Warnings:
Note 1003 select '1' AS `f1` from dual where 1
explain extended select * from t1 join t2 on f1=f2 where f1=1;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 system NULL NULL NULL NULL 1 100.00
1 SIMPLE t2 ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1003 select '1' AS `f1`,`test`.`t2`.`f2` AS `f2` from `test`.`t2` where (`test`.`t2`.`f2` = 1)
drop table t1,t2;
End of 5.1 tests.
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