drop table if exists t1,t2,t3; 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 3 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),(728912); 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 2 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 2 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 'b' 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 3 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; CREATE TABLE `job_titles` ( `job_title_id` int(6) unsigned NOT NULL default '0', `job_title` char(18) NOT NULL default '', PRIMARY KEY (`job_title_id`), UNIQUE KEY `job_title_id` (`job_title_id`,`job_title`) ) ENGINE=HEAP; SELECT MAX(job_title_id) FROM job_titles; MAX(job_title_id) NULL DROP TABLE job_titles; CREATE TABLE t1 (a INT NOT NULL, B INT, KEY(B)) ENGINE=HEAP; INSERT INTO t1 VALUES(1,1), (1,NULL); SELECT * FROM t1 WHERE B is not null; a B 1 1 DROP TABLE t1; CREATE TABLE t1 (pseudo char(35) PRIMARY KEY, date int(10) unsigned NOT NULL) ENGINE=HEAP; INSERT INTO t1 VALUES ('massecot',1101106491),('altec',1101106492),('stitch+',1101106304),('Seb Corgan',1101106305),('beerfilou',1101106263),('flaker',1101106529),('joce8',5),('M4vrick',1101106418),('gabay008',1101106525),('Vamp irX',1101106291),('ZoomZip',1101106546),('rip666',1101106502),('CBP ',1101106397),('guezpard',1101106496); DELETE FROM t1 WHERE date<1101106546; SELECT * FROM t1; pseudo date ZoomZip 1101106546 DROP TABLE t1; create table t1(a char(2)) engine=memory; insert into t1 values (NULL), (NULL); delete from t1 where a is null; insert into t1 values ('2'), ('3'); select * from t1; a 3 2 drop table t1; set storage_engine=HEAP; create table t1 (v varchar(10), c char(10), t varchar(50)); insert into t1 values('+ ', '+ ', '+ '); set @a=repeat(' ',20); insert into t1 values (concat('+',@a),concat('+',@a),concat('+',@a)); Warnings: Note 1265 Data truncated for column 'v' at row 1 select concat('*',v,'*',c,'*',t,'*') from t1; concat('*',v,'*',c,'*',t,'*') *+ *+*+ * *+ *+*+ * show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL ) ENGINE=MEMORY DEFAULT CHARSET=latin1 create table t2 like t1; show create table t2; Table Create Table t2 CREATE TABLE `t2` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL ) ENGINE=MEMORY DEFAULT CHARSET=latin1 create table t3 select * from t1; show create table t3; Table Create Table t3 CREATE TABLE `t3` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL ) ENGINE=MEMORY DEFAULT CHARSET=latin1 alter table t1 modify c varchar(10); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` varchar(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL ) ENGINE=MEMORY DEFAULT CHARSET=latin1 alter table t1 modify v char(10); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` char(10) DEFAULT NULL, `c` varchar(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL ) ENGINE=MEMORY DEFAULT CHARSET=latin1 alter table t1 modify t varchar(10); Warnings: Warning 1265 Data truncated for column 't' at row 2 show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` char(10) DEFAULT NULL, `c` varchar(10) DEFAULT NULL, `t` varchar(10) DEFAULT NULL ) ENGINE=MEMORY DEFAULT CHARSET=latin1 select concat('*',v,'*',c,'*',t,'*') from t1; concat('*',v,'*',c,'*',t,'*') *+*+*+ * *+*+*+ * drop table t1,t2,t3; create table t1 (v varchar(10), c char(10), t varchar(50), key(v), key(c), key(t(10))); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL, KEY `v` (`v`), KEY `c` (`c`), KEY `t` (`t`(10)) ) ENGINE=MEMORY DEFAULT CHARSET=latin1 select count(*) from t1; count(*) 270 insert into t1 values(concat('a',char(1)),concat('a',char(1)),concat('a',char(1))); select count(*) from t1 where v='a'; count(*) 10 select count(*) from t1 where c='a'; count(*) 10 select count(*) from t1 where t='a'; count(*) 10 select count(*) from t1 where v='a '; count(*) 10 select count(*) from t1 where c='a '; count(*) 10 select count(*) from t1 where t='a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; count(*) 10 select count(*) from t1 where v like 'a%'; count(*) 11 select count(*) from t1 where c like 'a%'; count(*) 11 select count(*) from t1 where t like 'a%'; count(*) 11 select count(*) from t1 where v like 'a %'; count(*) 9 explain select count(*) from t1 where v='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const 10 Using where explain select count(*) from t1 where c='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref c c 11 const 10 Using where explain select count(*) from t1 where t='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref t t 13 const 10 Using where explain select count(*) from t1 where v like 'a%'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ALL v NULL NULL NULL 271 Using where explain select count(*) from t1 where v between 'a' and 'a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const 10 Using where explain select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const 10 Using where alter table t1 add unique(v); ERROR 23000: Duplicate entry '{ ' for key 'v_2' select concat('*',v,'*',c,'*',t,'*') as qq from t1 where v='a' order by length(concat('*',v,'*',c,'*',t,'*')); qq *a*a*a* *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * explain select * from t1 where v='a'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const 10 Using where select v,count(*) from t1 group by v limit 10; v count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select v,count(t) from t1 group by v limit 10; v count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select v,count(c) from t1 group by v limit 10; v count(c) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result trim(v),count(t) from t1 group by v limit 10; trim(v) count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result trim(v),count(c) from t1 group by v limit 10; trim(v) count(c) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select c,count(*) from t1 group by c limit 10; c count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select c,count(t) from t1 group by c limit 10; c count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result c,count(t) from t1 group by c limit 10; c count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select t,count(*) from t1 group by t limit 10; t count(*) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select t,count(t) from t1 group by t limit 10; t count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 select sql_big_result trim(t),count(t) from t1 group by t limit 10; trim(t) count(t) a 1 a 10 b 10 c 10 d 10 e 10 f 10 g 10 h 10 i 10 drop table t1; create table t1 (a char(10), unique (a)); insert into t1 values ('a'); insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a' for key 'a' alter table t1 modify a varchar(10); insert into t1 values ('a '),('a '),('a '),('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' update t1 set a='a ' where a like 'a '; update t1 set a='a ' where a like 'a '; drop table t1; create table t1 (v varchar(10), c char(10), t varchar(50), key using btree (v), key using btree (c), key using btree (t(10))); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL, KEY `v` USING BTREE (`v`), KEY `c` USING BTREE (`c`), KEY `t` USING BTREE (`t`(10)) ) ENGINE=MEMORY DEFAULT CHARSET=latin1 select count(*) from t1; count(*) 270 insert into t1 values(concat('a',char(1)),concat('a',char(1)),concat('a',char(1))); select count(*) from t1 where v='a'; count(*) 10 select count(*) from t1 where c='a'; count(*) 10 select count(*) from t1 where t='a'; count(*) 10 select count(*) from t1 where v='a '; count(*) 10 select count(*) from t1 where c='a '; count(*) 10 select count(*) from t1 where t='a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a '; count(*) 10 select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; count(*) 10 explain select count(*) from t1 where v='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const # Using where explain select count(*) from t1 where c='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref c c 11 const # Using where explain select count(*) from t1 where t='a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref t t 13 const # Using where explain select count(*) from t1 where v like 'a%'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range v v 13 NULL # Using where explain select count(*) from t1 where v between 'a' and 'a '; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const # Using where explain select count(*) from t1 where v between 'a' and 'a ' and v between 'a ' and 'b\n'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const # Using where alter table t1 add unique(v); ERROR 23000: Duplicate entry '{ ' for key 'v_2' select concat('*',v,'*',c,'*',t,'*') as qq from t1 where v='a' order by length(concat('*',v,'*',c,'*',t,'*')); qq *a*a*a* *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * *a *a*a * explain select * from t1 where v='a'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 ref v v 13 const # Using where drop table t1; create table t1 (a char(10), unique using btree (a)) engine=heap; insert into t1 values ('a'); insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a' for key 'a' alter table t1 modify a varchar(10); insert into t1 values ('a '),('a '),('a '),('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' insert into t1 values ('a '); ERROR 23000: Duplicate entry 'a ' for key 'a' update t1 set a='a ' where a like 'a '; update t1 set a='a ' where a like 'a '; drop table t1; create table t1 (v varchar(10), c char(10), t varchar(50), key(v(5)), key(c(5)), key(t(5))); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(10) DEFAULT NULL, `c` char(10) DEFAULT NULL, `t` varchar(50) DEFAULT NULL, KEY `v` (`v`(5)), KEY `c` (`c`(5)), KEY `t` (`t`(5)) ) ENGINE=MEMORY DEFAULT CHARSET=latin1 drop table t1; create table t1 (v varchar(65530), key(v(10))); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `v` varchar(65530) DEFAULT NULL, KEY `v` (`v`(10)) ) ENGINE=MEMORY DEFAULT CHARSET=latin1 insert into t1 values(repeat('a',65530)); select length(v) from t1 where v=repeat('a',65530); length(v) 65530 drop table t1; set storage_engine=MyISAM; create table t1 (a bigint unsigned auto_increment primary key, b int, key (b, a)) engine=heap; insert t1 (b) values (1),(1),(1),(1),(1),(1),(1),(1); select * from t1; a b 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 drop table t1; create table t1 (a int not null, b int not null auto_increment, primary key(a, b), key(b)) engine=heap; insert t1 (a) values (1),(1),(1),(1),(1),(1),(1),(1); select * from t1; a b 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 drop table t1; create table t1 (a int not null, b int not null auto_increment, primary key(a, b)) engine=heap; ERROR 42000: Incorrect table definition; there can be only one auto column and it must be defined as a key create table t1 (c char(255), primary key(c(90))); insert into t1 values ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"); insert into t1 values ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"); ERROR 23000: Duplicate entry 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl' for key 'PRIMARY' drop table t1; CREATE TABLE t1 (a int, key(a)) engine=heap; insert into t1 values (0); delete from t1; select * from t1; a insert into t1 values (0), (1); select * from t1 where a = 0; a 0 drop table t1; create table t1 (c char(10)) engine=memory; create table t2 (c varchar(10)) engine=memory; show table status like 't_'; Name Engine Version Row_format Rows Avg_row_length Data_length Max_data_length Index_length Data_free Auto_increment Create_time Update_time Check_time Collation Checksum Create_options Comment t1 MEMORY 10 Fixed 0 11 0 # 0 0 NULL NULL NULL NULL latin1_swedish_ci NULL t2 MEMORY 10 Fixed 0 12 0 # 0 0 NULL NULL NULL NULL latin1_swedish_ci NULL drop table t1, t2;