mysql 数据操作 单表查询 简单查询 避免重复DISTINCT

创建数据库company

create database company charset=utf8;

use company;

company.employee
    员工id      id                  int
    姓名        emp_name            varchar
    性别        sex                 enum
    年龄        age                 int
    入职日期     hire_date           date
    岗位        post                varchar
    职位描述     post_comment        varchar
    薪水        salary              double
    办公室       office              int
    部门编号     depart_id           int

#创建表

create table employee(
id int not null unique auto_increment,
name varchar(20) not null,
sex enum('male','female') not null default 'male',
age int(3) unsigned not null default 28,
hire_date date not null,
post varchar(50),
post_comment varchar(100),
salary double(15,2),
office int,
depart_id int
);

#查看表结构

mysql> desc employee;
+--------------+-----------------------+------+-----+---------+----------------+
| Field        | Type                  | Null | Key | Default | Extra          |
+--------------+-----------------------+------+-----+---------+----------------+
| id           | int(11)               | NO   | PRI | NULL    | auto_increment |
| name         | varchar(20)           | NO   |     | NULL    |                |
| sex          | enum('male','female') | NO   |     | male    |                |
| age          | int(3) unsigned       | NO   |     | 28      |                |
| hire_date    | date                  | NO   |     | NULL    |                |
| post         | varchar(50)           | YES  |     | NULL    |                |
| post_comment | varchar(100)          | YES  |     | NULL    |                |
| salary       | double(15,2)          | YES  |     | NULL    |                |
| office       | int(11)               | YES  |     | NULL    |                |
| depart_id    | int(11)               | YES  |     | NULL    |                |
+--------------+-----------------------+------+-----+---------+----------------+
10 rows in set (0.24 sec)

#插入记录
#三个部门：教学，销售，运营

insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values
('alex','male',78,'','teacher',1000000.31,401,1),
('yuanhao','male',73,'','teacher',3500,401,1),
('liwenzhou','male',28,'','teacher',2100,401,1),
('jingliyang','female',18,'','teacher',9000,401,1),
('jinxin','male',18,'','teacher',30000,401,1),
('成龙','male',48,'','teacher',10000,401,1),('歪歪','female',48,'','sale',3000.13,402,2),#以下是销售部门
('丫丫','female',38,'','sale',2000.35,402,2),
('丁丁','female',18,'','sale',1000.37,402,2),
('星星','female',18,'','sale',3000.29,402,2),
('格格','female',28,'','sale',4000.33,402,2),('张野','male',28,'','operation',10000.13,403,3), #以下是运营部门
('程咬金','male',18,'','operation',20000,403,3),
('程咬银','female',18,'','operation',19000,403,3),
('程咬铜','male',18,'','operation',18000,403,3),
('程咬铁','female',18,'','operation',17000,403,3)
;

#ps：如果在windows系统中，插入中文字符，select的结果为空白，可以将所有字符编码统一设置成gbk

#简单查询

SELECT id,name,sex,age,hire_date,post,post_comment,salary,office,depart_id
    FROM employee;    SELECT * FROM employee;    SELECT name,salary FROM employee;

查看有哪些职位

mysql> select post from employee;
+-----------+
| post      |
+-----------+
| teacher   |
| teacher   |
| teacher   |
| teacher   |
| teacher   |
| teacher   |
| sale      |
| sale      |
| sale      |
| sale      |
| sale      |
| operation |
| operation |
| operation |
| operation |
| operation |
+-----------+
16 rows in set (0.00 sec)

#避免重复DISTINCT

mysql> select distinct post from employee;
+-----------+
| post      |
+-----------+
| teacher   |
| sale      |
| operation |
+-----------+
3 rows in set (0.00 sec)