Question

mysql怎么指定查询一张表的查询结果，如最后5行记录和最前5行记录

Answer 1

mysql如何指定查询一张表的查询结果，如最后5行记录和最前5行记录

mysql如何指定查询一张表的查询结果，如最后5行记录和最前5行记录
我们以student表为例，里面有三个字段：id,name,age，其中id为主健，为自增，里面共有10条记录，如下所示。
mysql> select * from student;
+----+------+------+
| id | name | age |
+----+------+------+
| 1 | li | 11 |
| 2 | zh | 12 |
| 3 | chou | 13 |
| 4 | he | 14 |
| 5 | lin | 15 |
| 6 | ll | 16 |
| 7 | chen | 17 |
| 8 | yu | 18 |
| 9 | wu | 19 |
| 10 | xie | 20 |
+----+------+------+
10 rows in set (0.00 sec)

1、查询第一行记录
select * from student limit 1;
+----+------+------+
| id | name | age |
+----+------+------+
| 1 | li | 11 |
+----+------+------+
1 row in set (0.00 sec)

2、查询最后一行记录
select * from student order by id desc limit 1;
+----+------+------+
| id | name | age |
+----+------+------+
| 10 | xie | 20 |
+----+------+------+
1 row in set (0.00 sec)

3、查询前n行记录，如前5行
select * from student limit 5;
select * from student limit 0,5;
select * from student order by id asc limit 5;
上面三条语句的结果都是一样的，如下：
+----+------+------+
| id | name | age |
+----+------+------+
| 1 | li | 11 |
| 2 | zh | 12 |
| 3 | chou | 13 |
| 4 | he | 14 |
| 5 | lin | 15 |
+----+------+------+
5 rows in set (0.00 sec)

4、查询后n行记录，如后5条，注意结果为倒序排序，因为用了desc
select * from student order by id desc limit 5;
+----+------+------+
| id | name | age |
+----+------+------+
| 10 | xie | 20 |
| 9 | wu | 19 |
| 8 | yu | 18 |
| 7 | chen | 17 |
| 6 | ll | 16 |
+----+------+------+
5 rows in set (0.00 sec)

5、查询第m行到第n行记录，注意表中的记录下标是从0开始的，就像数组一样
select * from student limit m,n; 返回m+1到m+n行记录,m代表开始的下标，n代表查找的结果数，将返回n行结果
select * from student limit 2,8; 返回3到10行记录
+----+------+------+
| id | name | age |
+----+------+------+
| 3 | chou | 13 |
| 4 | he | 14 |
| 5 | lin | 15 |
| 6 | ll | 16 |
| 7 | chen | 17 |
| 8 | yu | 18 |
| 9 | wu | 19 |
| 10 | xie | 20 |
+----+------+------+
8 rows in set (0.00 sec)

select * from student limit 3,1; 返回第4行
+----+------+------+
| id | name | age |
+----+------+------+
| 4 | he | 14 |
+----+------+------+
1 row in set (0.00 sec)

6、查询一条记录($id)的下一条记录
select * from student where id>$id order by id asc limit 1;
如$id=4时将返回第5条记录
select * from student where id>4 order by id asc limit 1;
+----+------+------+
| id | name | age |
+----+------+------+
| 5 | lin | 15 |
+----+------+------+
1 row in set (0.00 sec)

7、查询一条记录($id)的上一条记录
select * from student where id<$id order by id desc limit 1;
如$id=4时将返回第3条记录
select * from student where id<4 order by id desc limit 1;
+----+------+------+
| id | name | age |
+----+------+------+
| 3 | chou | 13 |
+----+------+------+
1 row in set (0.00 sec)