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drop table if exists t1;
create TEMPORARY table t1 (id int not null, str char(10), unique(str)) ENGINE=MYISAM;
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 43 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 43 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 43 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 TEMPORARY table t1 (a int not null) ENGINE=myisam;
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;
create TEMPORARY table ☃ (☢ int, ☣ int, key ☢ (☢), key ☣ (☢,☣)) ENGINE=MYISAM;
insert into ☃ (☢) values (1);
insert into ☃ (☢) values (2);
explain select ☢ from ☃ where ☢=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE ☃ ref ☢,☣ ☢ 5 const 1 Using where; Using index
drop table ☃;
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(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;
End of 5.0 tests.
explain select 1;
Catalog Database Table Table_alias Column Column_alias Type Length Max length Is_null Flags Decimals Charsetnr
def id 5 3 1 N 32897 0 63
def select_type 8 76 6 N 1 31 45
def table 8 256 0 Y 0 31 45
def type 8 40 0 Y 0 31 45
def possible_keys 8 16384 0 Y 0 31 45
def key 8 256 0 Y 0 31 45
def key_len 8 1280 0 Y 0 31 45
def ref 8 4096 0 Y 0 31 45
def rows 5 10 0 Y 32896 0 63
def Extra 8 1020 14 N 1 31 45
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
End of 5.2 tests.
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