Mysql中Identity 详细介绍

mysql> create table test_myisam (id int not null auto_increment primary key, name char(5)) engine=myisam;Query OK, 0 rows affected (0.04 sec)mysql> insert into test_myisam (name) select ‘a‘;Query OK, 1 row affected (0.00 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> insert into test_myisam (name) select ‘b‘;Query OK, 1 row affected (0.00 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> insert into test_myisam (name) select ‘c‘;Query OK, 1 row affected (0.00 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> insert into test_myisam (name) select name from test_myisam;Query OK, 3 rows affected (0.00 sec)Records: 3 Duplicates: 0 Warnings: 0mysql> select * from test_myisam;+----+------+| id | name |+----+------+| 1 | a  || 2 | b  || 3 | c  || 4 | a  || 5 | b  || 6 | c  |+----+------+6 rows in set (0.00 sec)mysql> delete from test_myisam where id=6;Query OK, 1 row affected (0.00 sec)

mysql> insert into test_myisam(name) select ‘d‘;Query OK, 1 row affected (0.00 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> select * from test_myisam;+----+------+| id | name |+----+------+| 1 | a  || 2 | b  || 3 | c  || 4 | a  || 5 | b  || 7 | d  |+----+------+6 rows in set (0.00 sec)

mysql> create table test_innodb(id int not null auto_increment primary key, name char(5)) engine=innodb;Query OK, 0 rows affected (0.26 sec)mysql> insert into test_innodb (name)select ‘a‘;Query OK, 1 row affected (0.06 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> insert into test_innodb (name)select ‘b‘;Query OK, 1 row affected (0.06 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> insert into test_innodb (name)select ‘c‘;Query OK, 1 row affected (0.07 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> select * from test_innodb;+----+------+| id | name |+----+------+| 1 | a  || 2 | b  || 3 | c  |+----+------+3 rows in set (0.00 sec)mysql> delete from test_innodb where id=3;Query OK, 1 row affected (0.05 sec)mysql> insert into test_innodb (name)select ‘d‘;Query OK, 1 row affected (0.20 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> select * from test_innodb;+----+------+| id | name |+----+------+| 1 | a  || 2 | b  || 4 | d  |+----+------+3 rows in set (0.00 sec)mysql> exitBye[2@a data]$ mysql -uroot -pwsdadWelcome to the MySQL monitor. Commands end with ; or /g.Your MySQL connection id is 5Server version: 5.5.37-log Source distributionCopyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type ‘help;‘ or ‘/h‘ for help. Type ‘/c‘ to clear the current input statement.mysql> use wisonDatabase changedmysql> delete from test_innodb where id=4;Query OK, 1 row affected (0.07 sec)mysql> exitBye[2@a data]$ sudo service mysql restartShutting down MySQL... SUCCESS!Starting MySQL.. SUCCESS![2@a data]$ mysql -uroot -pwisonWelcome to the MySQL monitor. Commands end with ; or /g.Your MySQL connection id is 1Server version: 5.5.37-log Source distributionCopyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type ‘help;‘ or ‘/h‘ for help. Type ‘/c‘ to clear the current input statement.mysql> use wisonDatabase changedmysql> insert into test_innodb (name) select ‘z‘;Query OK, 1 row affected (0.07 sec)Records: 1 Duplicates: 0 Warnings: 0mysql> select * from test_innodb;+----+------+| id | name |+----+------+| 1 | a  || 2 | b  || 3 | z  |+----+------+3 rows in set (0.00 sec)