显示查询记录的前n条 mysql limit用法

mysql> select id,id_no from torder where user = 8  order by createtime desc ;
+----+------------------+
| id | id_no            |
+----+------------------+
| 12 | 2015072609100000 |
| 23 | 2015072816100000 |
| 22 | 2015072816100000 |
| 21 | 2015072816100000 |
| 20 | 2015072815100000 |
| 19 | 2015072815100000 |
| 18 | 2015072814100000 |
| 17 | 2015072810100000 |
| 16 | 2015072810100000 |
| 15 | 2015072720100000 |
| 14 | 2015072720100000 |
| 13 | 2015072609100000 |
| 10 | NULL             |
|  8 | NULL             |
|  7 | NULL             |
|  4 | NULL             |
|  9 | NULL             |
| 11 | 2015072220100000 |
+----+------------------+
18 rows in set

mysql> select id,id_no from torder where user = 8 order by createtime desc limit 5;
+----+------------------+
| id | id_no            |
+----+------------------+
| 12 | 2015072609100000 |
| 23 | 2015072816100000 |
| 22 | 2015072816100000 |
| 21 | 2015072816100000 |
| 20 | 2015072815100000 |
+----+------------------+
5 rows in set