drop table if exists t1;
create table t1 (a int not null,b int not null, primary key (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	NULL	NULL	NULL	NULL		HASH	
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 (c,a);
drop table t1;
create table t1 (a int not null,b int not null, primary key (a)) engine=memory comment="testing heaps";
insert into t1 values(1,1),(2,2),(3,3),(4,4);
delete from t1 where a > 0;
select * from t1;
a	b
drop table t1;
create table t1 (a int not null,b int not null, primary key (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(a);
select * from t1 where a > 736494;
a
869751
802616
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	range	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 (x), unique y (y))
engine=heap;
insert into t1 values (1,1),(2,2),(1,3),(2,4),(2,5),(2,6);
select * from t1 where x=1;
x	y
1	3
1	1
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(a),  key(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	6
1	5
1	4
1	3
1	2
1	1
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	6
1	5
1	4
1	3
1	2
1	1
1	6
1	5
1	4
1	3
1	2
1	1
drop table t1;
create table t1 (id int unsigned not null, primary key (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(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 "q%";
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	btn	NULL	NULL	NULL	14	Using where
select * from t1 where btn like "q%";
btn
alter table t1 add column new_col char(1) not null, add key (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	ALL	btn	NULL	NULL	NULL	11	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	10	Using where
drop table t1;
CREATE TABLE t1 (
a int default NULL,
b int default NULL,
KEY a (a),
UNIQUE b (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	10	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 default NULL,
key a (a)
) ENGINE=HEAP;
INSERT INTO t1 VALUES (10), (10), (10);
EXPLAIN SELECT * FROM t1 WHERE a=10;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ref	a	a	5	const	10	Using where
SELECT * FROM t1 WHERE a=10;
a
10
10
10
DROP TABLE t1;
CREATE TABLE t1 (a int not null, primary key(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;