MySql的基本操作

Posted 2020-10-14 从程序员到外卖小哥

1. 查询数据：select * from xxx;

   例子：

   （1）select id,username,password from t_user;

   （2）select id,username,password,gender from t_user where gender = ‘男‘;

   （3）select id,username,password,gender from t_user where gender is null;

2.  

   添加数据：insert xxx(id, username) values(xx, "xxx");

   例子：

   insert into t_user(id, username) values(10, "hehehe");

   insert into t_user(id, gender, username, age, password) values(15, ‘男‘, ‘shihu‘, 18, ‘123456‘);

   insert into t_user values(16, ‘benladeng‘, ‘123456‘, ‘拉登‘, ‘nan‘, 18);

3.  

   修改数据：update tablename set xx=xx,xxx=xx where xxx=xxx and xxx=xxx;

4.  

   删除数据：delete from tablename where xx=xxx and xxx = xxx or xxx = xxx;

5.  

   DQL数据查询语言

   连接查询

      左外连接

         select

    e.name ename,

    e.gender,

    d.name dname

         from

    t_employee e left outer join t_department d

    on

    e.depart_id = d.id