在插入到MySQL数据库表中之前，有时候需要事先获取插入id以便完成一些跟插入id相关的操作，可以用以下方式完成。
MySQL把这些“相关信息”保存在数据库 `information_schema` 的表 `tables` 中，所以查询此表的相关字段即可。
该表的结构：
mysql> use information_schema; Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed mysql> SHOW COLUMNS FROM tables; +-----------------+---------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------------+---------------------+------+-----+---------+-------+ | TABLE_CATALOG | varchar(512) | NO | | | | | TABLE_SCHEMA | varchar(64) | NO | | | | | TABLE_NAME | varchar(64) | NO | | | | | TABLE_TYPE | varchar(64) | NO | | | | | ENGINE | varchar(64) | YES | | NULL | | | VERSION | bigint(21) unsigned | YES | | NULL | | | ROW_FORMAT | varchar(10) | YES | | NULL | | | TABLE_ROWS | bigint(21) unsigned | YES | | NULL | | | AVG_ROW_LENGTH | bigint(21) unsigned | YES | | NULL | | | DATA_LENGTH | bigint(21) unsigned | YES | | NULL | | | MAX_DATA_LENGTH | bigint(21) unsigned | YES | | NULL | | | INDEX_LENGTH | bigint(21) unsigned | YES | | NULL | | | DATA_FREE | bigint(21) unsigned | YES | | NULL | | | AUTO_INCREMENT | bigint(21) unsigned | YES | | NULL | | | CREATE_TIME | datetime | YES | | NULL | | | UPDATE_TIME | datetime | YES | | NULL | | | CHECK_TIME | datetime | YES | | NULL | | | TABLE_COLLATION | varchar(32) | YES | | NULL | | | CHECKSUM | bigint(21) unsigned | YES | | NULL | | | CREATE_OPTIONS | varchar(255) | YES | | NULL | | | TABLE_COMMENT | varchar(2048) | NO | | | | +-----------------+---------------------+------+-----+---------+-------+ 21 rows in set (0.03 sec)
可以看到，表的名字、版本、创建时间、最后更新时间、AUTO_INCREMENT等都显示在这里了。
所以，要查询 AUTO_INCREMENT 的值就可以像这样：
mysql> SELECT AUTO_INCREMENT FROM information_schema.tables
> WHERE table_schema='数据库名'
> AND table_name = '表名';
+----------------+
| AUTO_INCREMENT |
+----------------+
| 539 |
+----------------+
1 row in set (0.00 sec)