用COUNT来查询一个表的记录多少，小的时候无所谓，记录多的时候速度就是个问题。此刻表引擎为MyISAM. mysql> desc content; +---------+------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+------------+------+-----+---------+-------+ | cid | int(11) | NO | | 0 | | | aid | int(11) | YES | | NULL | | | content | mediumtext | YES | | NULL | | +---------+------------+------+-----+---------+-------+ 3 rows in set (0.02 sec) mysql> select count(*) from content; +----------+ | count(*) | +----------+ | 208081 | +----------+ 1 row in set (0.05 sec) 更新为INNODB. mysql> alter table content engine innodb; Query OK, 208081 rows affected (2 min 19.80 sec) Records: 208081 Duplicates: 0 Warnings: 0 mysql> select count(*) from content; +----------+ | count(*) | +----------+ | 208081 | +----------+ 1 row in set (33.99 sec) 新建立一个表专门存储记录的多少。如果要存放多个表的记录数目，以后增加相应的字段就可以了。 create table t_count (count_content int not null default 0); insert into t_count(count_content) select count(*) from content; DELIMITER $$ CREATE TRIGGER `tr_count_insert` AFTER INSERT on `content` FOR EACH ROW BEGIN   update t_count set count_content = count_content + 1; END$$ DELIMITER ; DELIMITER $$ CREATE TRIGGER `tr_count_delete` AFTER DELETE on `content` FOR EACH ROW BEGIN   update t_count set count_content = count_content - 1; END$$ DELIMITER ; 这样虽然对数据更新操作有性能上的影响，不过查询速度就非常快了。因为这个表无论如何只有一条记录。 mysql> delete from content limit 1; Query OK, 1 row affected (0.06 sec) mysql> select count(*) from content; +----------+ | count(*) | +----------+ | 208080 | +----------+ 1 row in set (37.79 sec) mysql> select count_content from t_count; +---------------+ | count_content | +---------------+ | 208080 | +---------------+ 1 row in set (0.01 sec)

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