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drop table if exists t1;
create table t1 (a int not null,b int not null, primary key using BTREE (a)) engine=heap comment="testing heaps" avg_row_length=100 min_rows=1 max_rows=100;
insert into t1 values(1,1),(2,2),(3,3),(4,4);
delete from t1 where a=1 or a=0;
show keys from t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
t1 0 PRIMARY 1 a A NULL NULL NULL BTREE
select * from t1;
a b
2 2
3 3
4 4
select * from t1 where a=4;
a b
4 4
update t1 set b=5 where a=4;
update t1 set b=b+1 where a>=3;
replace t1 values (3,3);
select * from t1;
a b
2 2
3 3
4 6
alter table t1 add c int not null, add key using BTREE (c,a);
drop table t1;
create table t1 (a int not null,b int not null, primary key using BTREE (a)) engine=heap comment="testing heaps";
insert into t1 values(-2,-2),(-1,-1),(0,0),(1,1),(2,2),(3,3),(4,4);
delete from t1 where a > -3;
select * from t1;
a b
drop table t1;
create table t1 (a int not null,b int not null, primary key using BTREE (a)) engine=heap comment="testing heaps";
insert into t1 values(1,1),(2,2),(3,3),(4,4);
alter table t1 modify a int not null auto_increment, engine=myisam, comment="new myisam table";
select * from t1;
a b
1 1
2 2
3 3
4 4
drop table t1;
create table t1 (a int not null) engine=heap;
insert into t1 values (869751),(736494),(226312),(802616);
select * from t1 where a > 736494;
a
869751
802616
alter table t1 add unique uniq_id using BTREE (a);
select * from t1 where a > 736494;
a
802616
869751
select * from t1 where a = 736494;
a
736494
select * from t1 where a=869751 or a=736494;
a
736494
869751
select * from t1 where a in (869751,736494,226312,802616);
a
226312
736494
802616
869751
alter table t1 engine=myisam;
explain select * from t1 where a in (869751,736494,226312,802616);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index uniq_id uniq_id 4 NULL 4 Using where; Using index
drop table t1;
create table t1 (x int not null, y int not null, key x using BTREE (x,y), unique y using BTREE (y))
engine=heap;
insert into t1 values (1,1),(2,2),(1,3),(2,4),(2,5),(2,6);
explain select * from t1 where x=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref x x 4 const 1
select * from t1 where x=1;
x y
1 1
1 3
select * from t1,t1 as t2 where t1.x=t2.y;
x y x y
1 1 1 1
2 2 2 2
1 3 1 1
2 4 2 2
2 5 2 2
2 6 2 2
explain select * from t1,t1 as t2 where t1.x=t2.y;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL x NULL NULL NULL 6
1 SIMPLE t2 eq_ref y y 4 test.t1.x 1
drop table t1;
create table t1 (a int) engine=heap;
insert into t1 values(1);
select max(a) from t1;
max(a)
1
drop table t1;
CREATE TABLE t1 ( a int not null default 0, b int not null default 0, key using BTREE (a,b), key using BTREE (b) ) ENGINE=HEAP;
insert into t1 values(1,1),(1,2),(2,3),(1,3),(1,4),(1,5),(1,6);
select * from t1 where a=1;
a b
1 1
1 2
1 3
1 4
1 5
1 6
insert into t1 values(1,1),(1,2),(2,3),(1,3),(1,4),(1,5),(1,6);
select * from t1 where a=1;
a b
1 1
1 1
1 2
1 2
1 3
1 3
1 4
1 4
1 5
1 5
1 6
1 6
explain select * from tx where a=x order by a,b;
id select_type table type possible_keys key key_len ref rows Extra
x SIMPLE tx ref a a x const x Using where
explain select * from tx where a=x order by b;
id select_type table type possible_keys key key_len ref rows Extra
x SIMPLE tx ref a a x const x Using where
select * from t1 where b=1;
a b
1 1
1 1
explain select * from tx where b=x;
id select_type table type possible_keys key key_len ref rows Extra
x SIMPLE tx ref b b x const x
drop table t1;
create table t1 (id int unsigned not null, primary key using BTREE (id)) engine=HEAP;
insert into t1 values(1);
select max(id) from t1;
max(id)
1
insert into t1 values(2);
select max(id) from t1;
max(id)
2
replace into t1 values(1);
drop table t1;
create table t1 (n int) engine=heap;
drop table t1;
create table t1 (n int) engine=heap;
drop table if exists t1;
CREATE table t1(f1 int not null,f2 char(20) not
null,index(f2)) engine=heap;
INSERT into t1 set f1=12,f2="bill";
INSERT into t1 set f1=13,f2="bill";
INSERT into t1 set f1=14,f2="bill";
INSERT into t1 set f1=15,f2="bill";
INSERT into t1 set f1=16,f2="ted";
INSERT into t1 set f1=12,f2="ted";
INSERT into t1 set f1=12,f2="ted";
INSERT into t1 set f1=12,f2="ted";
INSERT into t1 set f1=12,f2="ted";
delete from t1 where f2="bill";
select * from t1;
f1 f2
16 ted
12 ted
12 ted
12 ted
12 ted
drop table t1;
create table t1 (btn char(10) not null, key using BTREE (btn)) engine=heap;
insert into t1 values ("hello"),("hello"),("hello"),("hello"),("hello"),("a"),("b"),("c"),("d"),("e"),("f"),("g"),("h"),("i");
explain select * from t1 where btn like "i%";
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range btn btn 10 NULL 1 Using where
explain select * from t1 where btn like "h%";
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range btn btn 10 NULL # Using where
explain select * from t1 where btn like "a%";
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range btn btn 10 NULL 1 Using where
explain select * from t1 where btn like "b%";
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range btn btn 10 NULL 1 Using where
select * from t1 where btn like "ff%";
btn
select * from t1 where btn like " %";
btn
select * from t1 where btn like "q%";
btn
alter table t1 add column new_col char(1) not null, add key using BTREE (btn,new_col), drop key btn;
update t1 set new_col=left(btn,1);
explain select * from t1 where btn="a";
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref btn btn 10 const 1 Using where
explain select * from t1 where btn="a" and new_col="a";
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref btn btn 11 const,const 1 Using where
drop table t1;
CREATE TABLE t1 (
a int default NULL,
b int default NULL,
KEY a using BTREE (a),
UNIQUE b using BTREE (b)
) engine=heap;
INSERT INTO t1 VALUES (NULL,99),(99,NULL),(1,1),(2,2),(1,3);
SELECT * FROM t1 WHERE a=NULL;
a b
explain SELECT * FROM t1 WHERE a IS NULL;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref a a 5 const 1 Using where
SELECT * FROM t1 WHERE a<=>NULL;
a b
NULL 99
SELECT * FROM t1 WHERE b=NULL;
a b
explain SELECT * FROM t1 WHERE b IS NULL;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref b b 5 const 1 Using where
SELECT * FROM t1 WHERE b<=>NULL;
a b
99 NULL
INSERT INTO t1 VALUES (1,3);
ERROR 23000: Duplicate entry '3' for key 1
DROP TABLE t1;
CREATE TABLE t1 (a int, b int, c int, key using BTREE (a, b, c)) engine=heap;
INSERT INTO t1 VALUES (1, NULL, NULL), (1, 1, NULL), (1, NULL, 1);
SELECT * FROM t1 WHERE a=1 and b IS NULL;
a b c
1 NULL NULL
1 NULL 1
SELECT * FROM t1 WHERE a=1 and c IS NULL;
a b c
1 NULL NULL
1 1 NULL
SELECT * FROM t1 WHERE a=1 and b IS NULL and c IS NULL;
a b c
1 NULL NULL
DROP TABLE t1;
CREATE TABLE t1 (a int not null, primary key using BTREE (a)) engine=heap;
INSERT into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11);
DELETE from t1 where a < 100;
SELECT * from t1;
a
DROP TABLE t1;
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