今天利用limit offset,n从一个表中分批导出数据的时候，总比原表少那么几条记录，创建一个小表做测试才发现其中的奥秘：
mysql> select * from sss1;<br>+----+------+------+<br>| id | name | c_id |<br>+----+------+------+<br>| 1 | aaa | 1 | <br>| 2 | bbb | 2 | <br>| 3 | ccc | 3 | <br>| 4 | ddd | 1 | <br>| 5 | eee | 4 | <br>| 6 | ffff | 6 | <br>| 7 | NULL | 0 | <br>| 8 | NULL | 0 | <br>| 9 | NULL | 0 | <br>| 10 | ssss | 0 | <br>| 11 | ooo | 0 | <br>| 12 | 234 | 0 | <br>+----+------+------+<br>12 rows in set (0.00 sec)<br><br>mysql> select * from sss1 limit 0,3;<br>+----+------+------+<br>| id | name | c_id |<br>+----+------+------+<br>| 1 | aaa | 1 | <br>| 2 | bbb | 2 | <br>| 3 | ccc | 3 | <br>+----+------+------+<br>3 rows in set (0.00 sec)<br><br>mysql> select * from sss1 limit 4,6; <br>+----+------+------+<br>| id | name | c_id |<br>+----+------+------+<br>| 5 | eee | 4 | <br>| 6 | ffff | 6 | <br>| 7 | NULL | 0 | <br>| 8 | NULL | 0 | <br>| 9 | NULL | 0 | <br>| 10 | ssss | 0 | <br>+----+------+------+<br>6 rows in set (0.00 sec)
看明白了吗？
如果有offset的话，就会从offset+1条开始显示，越过第offset条，所以分批后我才会少几条记录，刚好是我的offset点，解决办法：offset 和上一条的n保持一致就行了：
mysql> select * from sss1;<br>+----+------+------+<br>| id | name | c_id |<br>+----+------+------+<br>| 1 | aaa | 1 | <br>| 2 | bbb | 2 | <br>| 3 | ccc | 3 | <br>| 4 | ddd | 1 | <br>| 5 | eee | 4 | <br>| 6 | ffff | 6 | <br>| 7 | NULL | 0 | <br>| 8 | NULL | 0 | <br>| 9 | NULL | 0 | <br>| 10 | ssss | 0 | <br>| 11 | ooo | 0 | <br>| 12 | 234 | 0 | <br>+----+------+------+<br>12 rows in set (0.00 sec)<br><br>mysql> select * from sss1 limit 0,3;<br>+----+------+------+<br>| id | name | c_id |<br>+----+------+------+<br>| 1 | aaa | 1 | <br>| 2 | bbb | 2 | <br>| 3 | ccc | 3 | <br>+----+------+------+<br>3 rows in set (0.00 sec)<br><br>mysql> select * from sss1 limit 3,6; <br>+----+------+------+<br>| id | name | c_id |<br>+----+------+------+<br>| 4 | ddd | 1 | <br>| 5 | eee | 4 | <br>| 6 | ffff | 6 | <br>| 7 | NULL | 0 | <br>| 8 | NULL | 0 | <br>| 9 | NULL | 0 | <br>+----+------+------+<br>6 rows in set (0.00 sec)
