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MYSQL获取自增ID的四种方法

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Jun 07, 2016 pm 03:19 PM

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欢迎进入Linux社区论坛，与200万技术人员互动交流 >>进入 1. select max(id) from tablename 2.SELECT LAST_INSERT_ID() 函数 LAST_INSERT_ID 是与table无关的，如果向表a插入数据后，再向表b插入数据，LAST_INSERT_ID会改变。在多用户交替插入数据的情况下

欢迎进入Linux社区论坛，与200万技术人员互动交流 >>进入

　　1. select max(id) from tablename

　　2.SELECT LAST_INSERT_ID() 函数

　　LAST_INSERT_ID 是与table无关的，如果向表a插入数据后，再向表b插入数据，LAST_INSERT_ID会改变。

　　在多用户交替插入数据的情况下max(id)显然不能用。这时就该使用LAST_INSERT_ID了，因为LAST_INSERT_ID是基于Connection的，只要每个线程都使用独立的 Connection对象，LAST_INSERT_ID函数将返回该Connection对AUTO_INCREMENT列最新的insert or update 操作生成的第一个record的ID。这个值不能被其它客户端（Connection）影响，保证了你能够找回自己的 ID 而不用担心其它客户端的活动，而且不需要加锁。使用单INSERT语句插入多条记录, LAST_INSERT_ID返回一个列表。

　　3. select @@IDENTITY;

　　@@identity 是表示的是最近一次向具有identity属性(即自增列)的表插入数据时对应的自增列的值，是系统定义的全局变量。一般系统定义的全局变量都是以@@开头，用户自定义变量以@开头。

　　比如有个表A，它的自增列是id，当向A表插入一行数据后，如果插入数据后自增列的值自动增加至101，则通过select @@identity得到的值就是101。使用@@identity的前提是在进行insert操作后，执行select @@identity的时候连接没有关闭，否则得到的将是NULL值。

　　4. SHOW TABLE STATUS;

　　得出的结果里边对应表名记录中有个Auto_increment字段，里边有下一个自增ID的数值就是当前该表的最大自增ID.

MYSQL获取自增ID的四种方法

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