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MySQL | DQL语句-简单查询

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MySQL

2025-08-05

MySQL安装教程

查询是SQL语言的核心，用于表达SQL查询的select查询命令是功能最强也是最为复杂的SQL语句，它的作用就是从数据库中检索数据，并将查询结果返回给用户。 select语句由：select子句(查询内容)、from子句(查询对象)、where子句(查询条件)、order by子句(排序方式)、group by子句(分组方式)等组成。查询语句属于SQL语句中的DQL语句，是所有SQL语句中最为复杂也是最重要的语句，所以必须掌握。接下来我们先从简单查询语句开始学习。

查一个字段

查询一个字段说的是：一个表有多列，查询其中的一列。

语法格式：select 字段名 from 表名;

SQL
select 字段名 from 表名;
  • select和from是关键字，不能随便写
  • 一条SQL语句必须以“;”结尾
  • 对于SQL语句来说，大小写都可以
  • 字段名和表名属于标识符，按照表的实际情况填写，不知道字段名的，可以使用desc命令查看表结构

案例1：查询公司中所有员工编号

SQL
select empno from emp;
SQL
mysql> desc emp;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| EMPNO    | int         | NO   | PRI | NULL    |       |
| ENAME    | varchar(10) | YES  |     | NULL    |       |
| JOB      | varchar(9)  | YES  |     | NULL    |       |
| MGR      | int         | YES  |     | NULL    |       |
| HIREDATE | date        | YES  |     | NULL    |       |
| SAL      | double(7,2) | YES  |     | NULL    |       |
| COMM     | double(7,2) | YES  |     | NULL    |       |
| DEPTNO   | int         | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
8 rows in set (0.00 sec)

mysql> select empno from emp;
+-------+
| empno |
+-------+
|  7369 |
|  7499 |
|  7521 |
|  7566 |
|  7654 |
|  7698 |
|  7782 |
|  7788 |
|  7839 |
|  7844 |
|  7876 |
|  7900 |
|  7902 |
|  7934 |
+-------+
14 rows in set (0.00 sec)

案例2：查询公司中所有员工姓名

SQL
select ename from emp;

SELECT ENAME FROM EMP; //大写小写都可以

seleCT Ename From emp; //大小写混合都可以

在mysql命令行客户端中，sql语句没有分号是不会执行的：

SQL
mysql> select empno from emp
    ->
    ->
    ->
    ->
    ->
    ->

末尾加上;就执行了：

SQL
mysql> select empno from emp
    ->
    ->
    ->
    ->
    ->
    ->
    -> ;
+-------+
| empno |
+-------+
|  7369 |
|  7499 |
|  7521 |
|  7566 |
|  7654 |
|  7698 |
|  7782 |
|  7788 |
|  7839 |
|  7844 |
|  7876 |
|  7900 |
|  7902 |
|  7934 |
+-------+
14 rows in set (0.00 sec)

以上sql虽然以分号结尾之后执行了，但是报错了，错误信息显示：语法错误。

假设一个SQL语句在书写过程中出错了，怎么终止这条SQL呢？\c

SQL
mysql> select   
    ->   empno
    -> froom ——>发现单词写错了
    -> \c

mysql> select empno from emp; //重新写

+-------+
| empno |
+-------+
|  7369 |
|  7499 |
|  7521 |
|  7566 |
|  7654 |
|  7698 |
|  7782 |
|  7788 |
|  7839 |
|  7844 |
|  7876 |
|  7900 |
|  7902 |
|  7934 |
+-------+
14 rows in set (0.00 sec)

任务1：查询所有部门名称。

SQL
mysql> desc dept;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| DEPTNO | int         | NO   | PRI | NULL    |       |
| DNAME  | varchar(14) | YES  |     | NULL    |       |
| LOC    | varchar(13) | YES  |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> select dname from dept;
+------------+
| dname      |
+------------+
| ACCOUNTING |
| RESEARCH   |
| SALES      |
| OPERATIONS |
+------------+
4 rows in set (0.00 sec)

任务2：查询所有薪资等级。

SQL
mysql> desc salgrade;
+-------+------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+------+------+-----+---------+-------+
| GRADE | int  | YES  |     | NULL    |       |
| LOSAL | int  | YES  |     | NULL    |       |
| HISAL | int  | YES  |     | NULL    |       |
+-------+------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> select grade from salgrade;
+-------+
| grade |
+-------+
|     1 |
|     2 |
|     3 |
|     4 |
|     5 |
+-------+
5 rows in set (0.00 sec)

查多个字段

查询多个字段时，在字段名和字段名之间添加“,”即可。

语法格式：select 字段名1,字段名2,字段名3 from 表名;

SQL
select 字段名1,字段名2,字段名3 from 表名;

案例1：查询员工编号以及员工姓名。

SQL
select empno, ename from emp;
SQL
mysql> desc emp;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| EMPNO    | int         | NO   | PRI | NULL    |       |
| ENAME    | varchar(10) | YES  |     | NULL    |       |
| JOB      | varchar(9)  | YES  |     | NULL    |       |
| MGR      | int         | YES  |     | NULL    |       |
| HIREDATE | date        | YES  |     | NULL    |       |
| SAL      | double(7,2) | YES  |     | NULL    |       |
| COMM     | double(7,2) | YES  |     | NULL    |       |
| DEPTNO   | int         | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
8 rows in set (0.01 sec)

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 (0.00 sec)

字段的前后顺序无所谓（只是显示结果列的时候顺序变了）：

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

任务1：查询部门编号、部门名称以及位置。

SQL
mysql> desc dept;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| DEPTNO | int         | NO   | PRI | NULL    |       |
| DNAME  | varchar(14) | YES  |     | NULL    |       |
| LOC    | varchar(13) | YES  |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.01 sec)

mysql> select deptno,dname,loc from dept;
+--------+------------+----------+
| deptno | dname      | loc      |
+--------+------------+----------+
|     10 | ACCOUNTING | NEW YORK |
|     20 | RESEARCH   | DALLAS   |
|     30 | SALES      | CHICAGO  |
|     40 | OPERATIONS | BOSTON   |
+--------+------------+----------+
4 rows in set (0.00 sec)

任务2：查询员工的名字以及工作岗位。

SQL
mysql> desc emp;
+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| EMPNO    | int         | NO   | PRI | NULL    |       |
| ENAME    | varchar(10) | YES  |     | NULL    |       |
| JOB      | varchar(9)  | YES  |     | NULL    |       |
| MGR      | int         | YES  |     | NULL    |       |
| HIREDATE | date        | YES  |     | NULL    |       |
| SAL      | double(7,2) | YES  |     | NULL    |       |
| COMM     | double(7,2) | YES  |     | NULL    |       |
| DEPTNO   | int         | YES  |     | NULL    |       |
+----------+-------------+------+-----+---------+-------+
8 rows in set (0.00 sec)

mysql> select ename,job from emp;
+--------+-----------+
| ename  | job       |
+--------+-----------+
| SMITH  | CLERK     |
| ALLEN  | SALESMAN  |
| WARD   | SALESMAN  |
| JONES  | MANAGER   |
| MARTIN | SALESMAN  |
| BLAKE  | MANAGER   |
| CLARK  | MANAGER   |
| SCOTT  | ANALYST   |
| KING   | PRESIDENT |
| TURNER | SALESMAN  |
| ADAMS  | CLERK     |
| JAMES  | CLERK     |
| FORD   | ANALYST   |
| MILLER | CLERK     |
+--------+-----------+
14 rows in set (0.00 sec)

查所有字段

查询所有字段的可以将每个字段都列出来查询，也可以采用“*”来代表所有字段

案例1：查询员工的所有信息

SQL
select * from emp;
SQL
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 (0.00 sec)

案例2：查询所有部门信息

SQL
select * from dept;
SQL
mysql> select * from dept;
+--------+------------+----------+
| DEPTNO | DNAME      | LOC      |
+--------+------------+----------+
|     10 | ACCOUNTING | NEW YORK |
|     20 | RESEARCH   | DALLAS   |
|     30 | SALES      | CHICAGO  |
|     40 | OPERATIONS | BOSTON   |
+--------+------------+----------+
4 rows in set (0.00 sec)

采用“*”进行查询存在的缺点：

  • select * from dept; 在执行的时候会被解析为 select DEPTNO, DNAME, LOC from dept; 再执行，所以这种效率方面弱一些。
  • 采用“*”的可读性较差，通过“*”很难看出都有哪些具体的字段。

什么时候使用“*”？

  • 这个SQL语句不在项目编码中使用，如果平时自己想快速查看表中所有数据的话，这种写法还是很给力的。

任务1：查询所有的薪资等级以及每个薪资等级的最低工资和最高工资。

SQL
select * from salgrade;
SQL
mysql> select * from salgrade;
+-------+-------+-------+
| GRADE | LOSAL | HISAL |
+-------+-------+-------+
|     1 |   700 |  1200 |
|     2 |  1201 |  1400 |
|     3 |  1401 |  2000 |
|     4 |  2001 |  3000 |
|     5 |  3001 |  9999 |
+-------+-------+-------+
5 rows in set (0.00 sec)

查询时字段可参与数学运算

在进行查询操作的时候，字段是可以参与数学运算的，例如加减乘除等。

案例1：查询每个员工的月薪

SQL
select ename, sal from emp;
SQL
mysql> select ename ,sal from emp;
+--------+---------+
| ename  | sal     |
+--------+---------+
| SMITH  |  800.00 |
| ALLEN  | 1600.00 |
| WARD   | 1250.00 |
| JONES  | 2975.00 |
| MARTIN | 1250.00 |
| BLAKE  | 2850.00 |
| CLARK  | 2450.00 |
| SCOTT  | 3000.00 |
| KING   | 5000.00 |
| TURNER | 1500.00 |
| ADAMS  | 1100.00 |
| JAMES  |  950.00 |
| FORD   | 3000.00 |
| MILLER | 1300.00 |
+--------+---------+
14 rows in set (0.00 sec)

案例2：查询每个员工的年薪（月薪 * 12）

SQL
select ename, sal * 12 from emp;
SQL
mysql> select ename ,sal*12 from emp;
+--------+----------+
| ename  | sal*12   |
+--------+----------+
| SMITH  |  9600.00 |
| ALLEN  | 19200.00 |
| WARD   | 15000.00 |
| JONES  | 35700.00 |
| MARTIN | 15000.00 |
| BLAKE  | 34200.00 |
| CLARK  | 29400.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
| TURNER | 18000.00 |
| ADAMS  | 13200.00 |
| JAMES  | 11400.00 |
| FORD   | 36000.00 |
| MILLER | 15600.00 |
+--------+----------+
14 rows in set (0.00 sec)

任务1：查询每个员工月薪加1000之后的月薪

SQL
select ename,sal+1000 from emp;
SQL
mysql> select ename ,sal+1000 from emp;
+--------+----------+
| ename  | sal+1000 |
+--------+----------+
| SMITH  |  1800.00 |
| ALLEN  |  2600.00 |
| WARD   |  2250.00 |
| JONES  |  3975.00 |
| MARTIN |  2250.00 |
| BLAKE  |  3850.00 |
| CLARK  |  3450.00 |
| SCOTT  |  4000.00 |
| KING   |  6000.00 |
| TURNER |  2500.00 |
| ADAMS  |  2100.00 |
| JAMES  |  1950.00 |
| FORD   |  4000.00 |
| MILLER |  2300.00 |
+--------+----------+
14 rows in set (0.00 sec)

任务2：查询每个员工月薪加1000之后的年薪

SQL
select ename,(sal+1000)*12 from emp;
SQL
mysql> select ename ,(sal+1000)*12 from emp;
+--------+---------------+
| ename  | (sal+1000)*12 |
+--------+---------------+
| SMITH  |      21600.00 |
| ALLEN  |      31200.00 |
| WARD   |      27000.00 |
| JONES  |      47700.00 |
| MARTIN |      27000.00 |
| BLAKE  |      46200.00 |
| CLARK  |      41400.00 |
| SCOTT  |      48000.00 |
| KING   |      72000.00 |
| TURNER |      30000.00 |
| ADAMS  |      25200.00 |
| JAMES  |      23400.00 |
| FORD   |      48000.00 |
| MILLER |      27600.00 |
+--------+---------------+
14 rows in set (0.00 sec)

查询时字段可起别名

我们借用一下之前的SQL语句

SQL
select ename, sal * 12 from emp;
SQL
mysql> select ename,sal * 12 from emp;
+--------+----------+
| ename  | sal * 12 |
+--------+----------+
| SMITH  |  9600.00 |
| ALLEN  | 19200.00 |
| WARD   | 15000.00 |
| JONES  | 35700.00 |
| MARTIN | 15000.00 |
| BLAKE  | 34200.00 |
| CLARK  | 29400.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
| TURNER | 18000.00 |
| ADAMS  | 13200.00 |
| JAMES  | 11400.00 |
| FORD   | 36000.00 |
| MILLER | 15600.00 |
+--------+----------+
14 rows in set (0.04 sec)

以上的查询结果列名“sal * 12”可读性较差，是否可以给查询结果的列名进行重命名呢？

as关键字

使用as关键字

SQL
select ename, sal * 12 as yearsal from emp;
SQL
mysql> select ename,sal * 12 as yearsal from emp;
+--------+----------+
| ename  | yearsal  |
+--------+----------+
| SMITH  |  9600.00 |
| ALLEN  | 19200.00 |
| WARD   | 15000.00 |
| JONES  | 35700.00 |
| MARTIN | 15000.00 |
| BLAKE  | 34200.00 |
| CLARK  | 29400.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
| TURNER | 18000.00 |
| ADAMS  | 13200.00 |
| JAMES  | 11400.00 |
| FORD   | 36000.00 |
| MILLER | 15600.00 |
+--------+----------+
14 rows in set (0.00 sec)

通过as关键字起别名后，查询结果列显示yearsal，可读性增强。

省略as关键字

其实as关键字可以省略，只要使用空格即可

SQL
select ename, sal * 12 yearsal from emp;
SQL
mysql> select ename,sal * 12 yearsal from emp;
+--------+----------+
| ename  | yearsal  |
+--------+----------+
| SMITH  |  9600.00 |
| ALLEN  | 19200.00 |
| WARD   | 15000.00 |
| JONES  | 35700.00 |
| MARTIN | 15000.00 |
| BLAKE  | 34200.00 |
| CLARK  | 29400.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
| TURNER | 18000.00 |
| ADAMS  | 13200.00 |
| JAMES  | 11400.00 |
| FORD   | 36000.00 |
| MILLER | 15600.00 |
+--------+----------+
14 rows in set (0.01 sec)

通过以上测试，得知as可以省略，可以使用空格代替as，但如果别名中有空格呢？

别名中有空格

SQL
select ename, sal * 12 year sal from emp;
SQL
mysql> select ename,sal * 12 year sal from emp;

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'sal from emp' at line 1

可以看出，执行报错了，说语法有问题，这是为什么？

分析一下：SQL语句编译器在检查该语句的时候，在year后面遇到了空格，会继续找from关键字，但year后面不是from关键字，所以编译器报错了。

怎么解决这个问题？

记住：如果别名中有空格的话，可以将这个别名使用双引号或者单引号将其括起来。

SQL
select ename, sal * 12 "year sal" from emp;
select ename, sal * 12 'year sal' from emp; ——>单引号是标准
SQL
mysql> select ename,sal * 12 "year sal" from emp;
+--------+----------+
| ename  | year sal |
+--------+----------+
| SMITH  |  9600.00 |
| ALLEN  | 19200.00 |
| WARD   | 15000.00 |
| JONES  | 35700.00 |
| MARTIN | 15000.00 |
| BLAKE  | 34200.00 |
| CLARK  | 29400.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
| TURNER | 18000.00 |
| ADAMS  | 13200.00 |
| JAMES  | 11400.00 |
| FORD   | 36000.00 |
| MILLER | 15600.00 |
+--------+----------+
14 rows in set (0.01 sec)


mysql> select ename,sal * 12 'year sal' from emp;
+--------+----------+
| ename  | year sal |
+--------+----------+
| SMITH  |  9600.00 |
| ALLEN  | 19200.00 |
| WARD   | 15000.00 |
| JONES  | 35700.00 |
| MARTIN | 15000.00 |
| BLAKE  | 34200.00 |
| CLARK  | 29400.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
| TURNER | 18000.00 |
| ADAMS  | 13200.00 |
| JAMES  | 11400.00 |
| FORD   | 36000.00 |
| MILLER | 15600.00 |
+--------+----------+
14 rows in set (0.00 sec)

在mysql中，字符串既可以使用双引号也可以使用单引号，但还是建议使用单引号，因为单引号属于标准SQL。

别名中有中文

如果别名采用中文呢？

SQL
select ename, sal * 12 年薪 from emp;
SQL
mysql> select ename,sal * 12 年薪 from emp;
+--------+----------+
| ename  | 年薪     |
+--------+----------+
| SMITH  |  9600.00 |
| ALLEN  | 19200.00 |
| WARD   | 15000.00 |
| JONES  | 35700.00 |
| MARTIN | 15000.00 |
| BLAKE  | 34200.00 |
| CLARK  | 29400.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
| TURNER | 18000.00 |
| ADAMS  | 13200.00 |
| JAMES  | 11400.00 |
| FORD   | 36000.00 |
| MILLER | 15600.00 |
+--------+----------+
14 rows in set (0.00 sec)

别名是中文是可以的，但是对于低版本的mysql来说会报错，需要添加双引号或单引号。 我们当前使用的mysql版本是：8.0.41,不会报错。

任务：查询所有员工的信息，要求每个字段(每一列的表头)名采用中文显示。

SQL
select empno 员工编号, ename 员工姓名, job 员工职位, mgr 上级编号, hiredate 入职日期, sal 工资, comm 奖金, deptno 部门编号 from emp;
SQL
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 (0.00 sec)

mysql> select empno 员工编号, ename 员工姓名, job 员工职位, mgr 上级编号, hiredate 入职日期, sal 工资, comm 奖金, deptno 部门编号 from emp;
+----------+----------+-----------+----------+------------+---------+---------+----------+
| 员工编号 | 员工姓名 | 员工职位  | 上级编号 | 入职日期   | 工资    | 奖金    | 部门编号 |
+----------+----------+-----------+----------+------------+---------+---------+----------+
|     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 (0.00 sec)

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