MySQL基础篇：轻松掌握简单查询技巧！

查询一个字段

mysql> select ENAME from EMP;
+--------+
| ENAME  |
+--------+
| SMITH  |
| ALLEN  |
| WARD   |
| JONES  |
| MARTIN |
| BLAKE  |
| CLARK  |
| SCOTT  |
| KING   |
| TURNER |
| ADAMS  |
| JAMES  |
| FORD   |
| MILLER |
+--------+
14 rows in set (0.52 sec)

mysql>

查询多个字段

查询员工的编号和姓名

mysql> select EMPNO,ENAME from EMP;
+-------+--------+
| EMPNO | ENAME  |
+-------+--------+
|  7369 | SMITH  |
|  7499 | ALLEN  |
|  7521 | WARD   |
|  7566 | JONES  |
|  7654 | MARTIN |
|  7698 | BLAKE  |
|  7782 | CLARK  |
|  7788 | SCOTT  |
|  7839 | KING   |
|  7844 | TURNER |
|  7876 | ADAMS  |
|  7900 | JAMES  |
|  7902 | FORD   |
|  7934 | MILLER |
+-------+--------+
14 rows in set (0.54 sec)

查询全部字段

可以将所有的字段放到select语句的后面，这种方案不方便，但是比较清楚，我们可以采用如下便捷的方式查询全部字段

mysql> select * from EMP;
+-------+--------+-----------+------+------------+---------+---------+--------+
| EMPNO | ENAME  | JOB       | MGR  | HIREDATE   | SAL     | COMM    | DEPTNO |
+-------+--------+-----------+------+------------+---------+---------+--------+
|  7369 | SMITH  | CLERK     | 7902 | 1980-12-17 |  800.00 | NULL    |     20 |
|  7499 | ALLEN  | SALESMAN  | 7698 | 1981-02-20 | 1600.00 |  300.00 |     30 |
|  7521 | WARD   | SALESMAN  | 7698 | 1981-02-22 | 1250.00 |  500.00 |     30 |
|  7566 | JONES  | MANAGER   | 7839 | 1981-04-02 | 2975.00 | NULL    |     20 |
|  7654 | MARTIN | SALESMAN  | 7698 | 1981-09-28 | 1250.00 | 1400.00 |     30 |
|  7698 | BLAKE  | MANAGER   | 7839 | 1981-05-01 | 2850.00 | NULL    |     30 |
|  7782 | CLARK  | MANAGER   | 7839 | 1981-06-09 | 2450.00 | NULL    |     10 |
|  7788 | SCOTT  | ANALYST   | 7566 | 1987-04-19 | 3000.00 | NULL    |     20 |
|  7839 | KING   | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL    |     10 |
|  7844 | TURNER | SALESMAN  | 7698 | 1981-09-08 | 1500.00 |    0.00 |     30 |
|  7876 | ADAMS  | CLERK     | 7788 | 1987-05-23 | 1100.00 | NULL    |     20 |
|  7900 | JAMES  | CLERK     | 7698 | 1981-12-03 |  950.00 | NULL    |     30 |
|  7902 | FORD   | ANALYST   | 7566 | 1981-12-03 | 3000.00 | NULL    |     20 |
|  7934 | MILLER | CLERK     | 7782 | 1982-01-23 | 1300.00 | NULL    |     10 |
+-------+--------+-----------+------+------------+---------+---------+--------+
14 rows in set (0.32 sec)

mysql>

计算员工的年薪

列出员工的编号，姓名和年薪

mysql> select EMPNO,ENAME,SAL*12 from EMP;
+-------+--------+----------+
| EMPNO | ENAME  | SAL*12   |
+-------+--------+----------+
|  7369 | SMITH  |  9600.00 |
|  7499 | ALLEN  | 19200.00 |
|  7521 | WARD   | 15000.00 |
|  7566 | JONES  | 35700.00 |
|  7654 | MARTIN | 15000.00 |
|  7698 | BLAKE  | 34200.00 |
|  7782 | CLARK  | 29400.00 |
|  7788 | SCOTT  | 36000.00 |
|  7839 | KING   | 60000.00 |
|  7844 | TURNER | 18000.00 |
|  7876 | ADAMS  | 13200.00 |
|  7900 | JAMES  | 11400.00 |
|  7902 | FORD   | 36000.00 |
|  7934 | MILLER | 15600.00 |
+-------+--------+----------+
14 rows in set (0.90 sec)

mysql>

将查询出来的字段显示为中文

mysql> select EMPNO as '员工编号',ENAME as '员工姓名', SAL*12 as '年薪' from EMP;
+----------+----------+----------+
| 员工编号 | 员工姓名 | 年薪     |
+----------+----------+----------+
|     7369 | SMITH    |  9600.00 |
|     7499 | ALLEN    | 19200.00 |
|     7521 | WARD     | 15000.00 |
|     7566 | JONES    | 35700.00 |
|     7654 | MARTIN   | 15000.00 |
|     7698 | BLAKE    | 34200.00 |
|     7782 | CLARK    | 29400.00 |
|     7788 | SCOTT    | 36000.00 |
|     7839 | KING     | 60000.00 |
|     7844 | TURNER   | 18000.00 |
|     7876 | ADAMS    | 13200.00 |
|     7900 | JAMES    | 11400.00 |
|     7902 | FORD     | 36000.00 |
|     7934 | MILLER   | 15600.00 |
+----------+----------+----------+
14 rows in set (0.39 sec)