1create table t1(a int(10)unsigned not null auto_increment primary key, 2b varchar(255) not null) engine=innodb default charset=utf8; 3insert into t1 values(1,'aaa'),(2,'bbb'); 4alter table t1 auto_increment=1; 5insert into t1 values(NULL, 'ccc'); 6select * from t1; 7a b 81 aaa 92 bbb 103 ccc 11drop table t1; 12