mysql 基本

客户端： navicat-管理工具，

1.主键 ： 唯一.性能高，

2.库-管理 表-存 字段 行

3.连接

//createConnection(哪台服务器, 用户名, 密码, 库)

var db=mysql.createConnection({host: 'localhost', user: 'root', password: 'a123456789', database: '20181105'});

4.关键字大小 字段加上 ` `

01.INSERT INTO `user_table` (`ID`, `username`, `password`) VALUES(0, 'blue2', '987654');

02.SELECT * FROM `user_table`;

03.SELECT * FROM student_table GROUP BY class;

04.SELECT class,AVG(score) FROM student_table GROUP BY class;

05.SELECT class,MAX(score),MIN(score) FROM student_table GROUP BY class;

06.根据名字求和

SELECT name,SUM(price) FROM sales_table GROUP BY name;

07.排序 降序

SELECT name,SUM(price) FROM sales_table GROUP BY name ORDER BY SUM(price) DESC;

08.排序 升序

SELECT name,SUM(price) FROM sales_table GROUP BY name ORDER BY SUM(price) ASC;

09.删选 合并 排序 限制

SELECT * FROM student_table WHERE score>60 GROUP BY class ORDER BY COUNT(class) DESC LIMIT 2;