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;