DQL语句-排序操作

MySQL | DQL语句-排序操作

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排序操作很常用，比如查询学员成绩，按照成绩降序排列。排序的SQL语法：

select .. from .. order by 字段 asc/desc

• select .. from ..：查询语句
• order by 字段：排序语句
• 字段：要排序的字段名
• asc：升序，默认排序方式
• desc：降序

单一字段升序

查询员工的编号、姓名、薪资，按照薪资升序排列。

select empno,ename,sal from emp order by sal asc;

mysql> select empno,ename,sal from emp order by sal asc;

+-------+--------+---------+
| empno | ename  | sal     |
+-------+--------+---------+
|  7369 | SMITH  |  800.00 |
|  7900 | JAMES  |  950.00 |
|  7876 | ADAMS  | 1100.00 |
|  7521 | WARD   | 1250.00 |
|  7654 | MARTIN | 1250.00 |
|  7934 | MILLER | 1300.00 |
|  7844 | TURNER | 1500.00 |
|  7499 | ALLEN  | 1600.00 |
|  7782 | CLARK  | 2450.00 |
|  7698 | BLAKE  | 2850.00 |
|  7566 | JONES  | 2975.00 |
|  7788 | SCOTT  | 3000.00 |
|  7902 | FORD   | 3000.00 |
|  7839 | KING   | 5000.00 |
+-------+--------+---------+
14 rows in set (0.00 sec)

单一字段降序

查询员工的编号、姓名、薪资，按照薪资降序排列。

select empno,ename,sal from emp order by sal desc;

mysql> select empno,ename,sal from emp order by sal desc;

+-------+--------+---------+
| empno | ename  | sal     |
+-------+--------+---------+
|  7839 | KING   | 5000.00 |
|  7788 | SCOTT  | 3000.00 |
|  7902 | FORD   | 3000.00 |
|  7566 | JONES  | 2975.00 |
|  7698 | BLAKE  | 2850.00 |
|  7782 | CLARK  | 2450.00 |
|  7499 | ALLEN  | 1600.00 |
|  7844 | TURNER | 1500.00 |
|  7934 | MILLER | 1300.00 |
|  7521 | WARD   | 1250.00 |
|  7654 | MARTIN | 1250.00 |
|  7876 | ADAMS  | 1100.00 |
|  7900 | JAMES  |  950.00 |
|  7369 | SMITH  |  800.00 |
+-------+--------+---------+
14 rows in set (0.00 sec)

默认采用升序

查询员工的编号、姓名、薪资，按照薪资升序排列。

select empno,ename,sal from emp order by sal;

mysql> select empno,ename,sal from emp order by sal;

+-------+--------+---------+
| empno | ename  | sal     |
+-------+--------+---------+
|  7369 | SMITH  |  800.00 |
|  7900 | JAMES  |  950.00 |
|  7876 | ADAMS  | 1100.00 |
|  7521 | WARD   | 1250.00 |
|  7654 | MARTIN | 1250.00 |
|  7934 | MILLER | 1300.00 |
|  7844 | TURNER | 1500.00 |
|  7499 | ALLEN  | 1600.00 |
|  7782 | CLARK  | 2450.00 |
|  7698 | BLAKE  | 2850.00 |
|  7566 | JONES  | 2975.00 |
|  7788 | SCOTT  | 3000.00 |
|  7902 | FORD   | 3000.00 |
|  7839 | KING   | 5000.00 |
+-------+--------+---------+
14 rows in set (0.00 sec)

查询员工的编号、姓名，按照姓名升序排列。

select empno,ename from emp order by ename;

mysql> select empno,ename from emp order by ename;

+-------+--------+
| empno | ename  |
+-------+--------+
|  7876 | ADAMS  |
|  7499 | ALLEN  |
|  7698 | BLAKE  |
|  7782 | CLARK  |
|  7902 | FORD   |
|  7900 | JAMES  |
|  7566 | JONES  |
|  7839 | KING   |
|  7654 | MARTIN |
|  7934 | MILLER |
|  7788 | SCOTT  |
|  7369 | SMITH  |
|  7844 | TURNER |
|  7521 | WARD   |
+-------+--------+
14 rows in set (0.00 sec)

多个字段排序

查询员工的编号、姓名、薪资，按照薪资升序排列，如果薪资相同的，再按照姓名升序排列。

select empno,ename,sal from emp order by sal asc, ename asc;

mysql> select empno,ename,sal from emp order by sal asc, ename asc;

+-------+--------+---------+
| empno | ename  | sal     |
+-------+--------+---------+
|  7369 | SMITH  |  800.00 |
|  7900 | JAMES  |  950.00 |
|  7876 | ADAMS  | 1100.00 |
|  7654 | MARTIN | 1250.00 |
|  7521 | WARD   | 1250.00 |
|  7934 | MILLER | 1300.00 |
|  7844 | TURNER | 1500.00 |
|  7499 | ALLEN  | 1600.00 |
|  7782 | CLARK  | 2450.00 |
|  7698 | BLAKE  | 2850.00 |
|  7566 | JONES  | 2975.00 |
|  7902 | FORD   | 3000.00 |
|  7788 | SCOTT  | 3000.00 |
|  7839 | KING   | 5000.00 |
+-------+--------+---------+
14 rows in set (0.00 sec)

where和order by的位置

找出岗位是MANAGER的员工姓名和薪资，按照薪资升序排列。

select ename,sal from emp where job = 'MANAGER' order by sal asc;

mysql> select ename,sal from emp where job = 'MANAGER' order by sal asc;
+-------+---------+
| ename | sal     |
+-------+---------+
| CLARK | 2450.00 |
| BLAKE | 2850.00 |
| JONES | 2975.00 |
+-------+---------+
3 rows in set (0.00 sec)

通过这个例子主要是想告诉大家：where先执行，order by语句是最后执行的。