drop table if exists t1,t2,t3; flush status; set autocommit=0; create table t1 (a int not null) engine=innodb; insert into t1 values (1),(2),(3); select * from t1; a 1 2 3 show status like "Qcache_queries_in_cache"; Variable_name Value Qcache_queries_in_cache 0 drop table t1; commit; set autocommit=1; begin; create table t1 (a int not null) engine=innodb; insert into t1 values (1),(2),(3); select * from t1; a 1 2 3 show status like "Qcache_queries_in_cache"; Variable_name Value Qcache_queries_in_cache 1 drop table t1; commit; create table t1 (a int not null) engine=innodb; create table t2 (a int not null) engine=innodb; create table t3 (a int not null) engine=innodb; insert into t1 values (1),(2); insert into t2 values (1),(2); insert into t3 values (1),(2); select * from t1; a 1 2 select * from t2; a 1 2 select * from t3; a 1 2 show status like "Qcache_queries_in_cache"; Variable_name Value Qcache_queries_in_cache 3 show status like "Qcache_hits"; Variable_name Value Qcache_hits 0 begin; select * from t1; a 1 2 select * from t2; a 1 2 select * from t3; a 1 2 show status like "Qcache_queries_in_cache"; Variable_name Value Qcache_queries_in_cache 3 show status like "Qcache_hits"; Variable_name Value Qcache_hits 3 insert into t1 values (3); insert into t2 values (3); insert into t1 values (4); select * from t1; a 1 2 3 4 select * from t2; a 1 2 3 select * from t3; a 1 2 show status like "Qcache_queries_in_cache"; Variable_name Value Qcache_queries_in_cache 1 show status like "Qcache_hits"; Variable_name Value Qcache_hits 4 commit; show status like "Qcache_queries_in_cache"; Variable_name Value Qcache_queries_in_cache 1 drop table t3,t2,t1; CREATE TABLE t1 (id int(11) NOT NULL auto_increment, PRIMARY KEY (id)) ENGINE=InnoDB; select count(*) from t1; count(*) 0 insert into t1 (id) values (0); select count(*) from t1; count(*) 1 drop table t1; set GLOBAL query_cache_size=1355776; CREATE TABLE t1 ( id int(10) NOT NULL auto_increment, a varchar(25) default NULL, PRIMARY KEY (id), UNIQUE KEY a (a)) ENGINE=innodb; CREATE TABLE t2 ( id int(10) NOT NULL auto_increment, b varchar(25) default NULL, PRIMARY KEY (id), UNIQUE KEY b (b)) ENGINE=innodb; CREATE TABLE t3 ( id int(10) NOT NULL auto_increment, t1_id int(10) NOT NULL default '0', t2_id int(10) NOT NULL default '0', state int(11) default NULL, PRIMARY KEY (id), UNIQUE KEY t1_id (t1_id,t2_id), KEY t2_id (t2_id,t1_id), CONSTRAINT `t3_ibfk_1` FOREIGN KEY (`t1_id`) REFERENCES `t1` (`id`), CONSTRAINT `t3_ibfk_2` FOREIGN KEY (`t2_id`) REFERENCES `t2` (`id`)) ENGINE=innodb; INSERT INTO t1 VALUES (1,'me'); INSERT INTO t2 VALUES (1,'you'); INSERT INTO t3 VALUES (2,1,1,2); delete from t3 where t1_id = 1 and t2_id = 1; select t1.* from t1, t2, t3 where t3.state & 1 = 0 and t3.t1_id = t1.id and t3.t2_id = t2.id and t1.id = 1 order by t1.a asc; id a begin; insert into t3 VALUES ( NULL, 1, 1, 2 ); insert into t3 VALUES ( NULL, 1, 1, 2 ); ERROR 23000: Duplicate entry '1-1' for key 2 commit; select t1.* from t1, t2, t3 where t3.state & 1 = 0 and t3.t1_id = t1.id and t3.t2_id = t2.id and t1.id = 1 order by t1.a asc; id a 1 me drop table t3,t2,t1;