use xia12;
CREATE TABLE IF NOT EXISTS course_info( stu_id INT NOT NULL,
course_id char(3) NOT NULL,
grade tinyint,
course_name varchar(20)NOT NULL,
foreign key(stu_id) references stu_info(stu_id),
/*foreign key(course_id) references course_info(course_id),*/
PRIMARY KEY(stu_id)
)ENGINE=InnoDB;
INSERT INTO course_info(stu_id,course_id,grade,course_name) 
VALUES(111545234,701,80,"操作系统");
INSERT INTO course_info(stu_id,course_id,grade,course_name) 
VALUES(111545235,701,30,"计算机网络");
INSERT INTO course_info(stu_id,course_id,grade,course_name) 
VALUES(111545236,701,90,"计算机基础");
INSERT INTO course_info(stu_id,course_id,grade,course_name) 
VALUES(111545237,701,96,"计算机网络");
INSERT INTO course_info(stu_id,course_id,grade,course_name) 
VALUES(111545238,705,89,"计算机基础"); 

//以上是course_id代码，先创建表，然后注释
use xia12;/*创建数据表*/CREATE TABLE IF NOT EXISTS stu_info(Stu_id INT NOT NULL PRIMARY KEY,stu_name VARCHAR(40) NOT NULL,age TINYINT UNSIGNED ,birthday timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,sex CHAR(2) DEFAULT '男' CHECK(sex='男' OR sex='女'),address CHAR(30),mark smallint,major CHAR(10),grade FLOAT(5,2),sdept VARCHAR(10))ENGINE=InnoDB;/*插入表数据,插入完之后，请注释掉，以免出现主键重复键入的错误*//*INSERT INTO stu_info(Stu_id,stu_name,age,birthday,sex,address,mark,major,grade,sdept) VALUES(111545234,"张雨",20,'1998-05-28',"男","江苏徐州",543,"C++",89.90,"信息学院");INSERT INTO stu_info(Stu_id,stu_name,age,birthday,sex,address,mark,major,grade,sdept) VALUES( 111545235,"何玉",24,'1994-06-27',"女","江苏宿迁",643,"MySql",79.90,"商学院");INSERT INTO stu_info(Stu_id,stu_name,age,birthday,sex,address,mark,major,grade,sdept) VALUES( 111545236,"王江",19,'1999-11-18',"男","江苏扬州",47,"PHP",59.60,"信息学院");INSERT INTO stu_info(Stu_id,stu_name,age,birthday,sex,address,mark,major,grade,sdept) VALUES( 111545237,"张帆",30,'1988-03-08',"女","江苏苏州",443,"Python",89.90,"电信学院");INSERT INTO stu_info(Stu_id,stu_name,age,birthday,sex,address,mark,major,grade,sdept) VALUES( 111545238,"梦凡",23,'1995-06-28',"男","江苏盐城",333,"PHP",95.90,"商学院");INSERT INTO stu_info(Stu_id,stu_name,age,birthday,sex,address,mark,major,grade,sdept) VALUES( 111545239,"刘留",20,'1998-05-28',"女","江苏南京",463,"JS",78.60,"信息学院");*/alter table stu_info modify birthday date NULL;/*修改列的属性*/select *FROM stu_info;/*查询所有列，*是通配符*//*查询指定列*/SELECT stu_id,stu_name,sex,age FROM stu_info;/*SELECT stu_id,stu_name,YEAR(GETDATE())-YEAR(birthday) FROM stu_info;存在问题getdate（）系统函数找不到*/SELECT age AS'年龄'FROM stu_info;/*改变列标题显示 别名*/SELECT DISTINCT sdept FROM stu_info;/*distinct删除重复行，去除结果重复的信息*/SELECT stu_id,stu_name,mark FROM stu_info WHERE 1=1 limit 3;/*返回查询的部分数据，不同的数据库，有不同的方法*/SELECT stu_id,stu_name,birthday,sex FROM stu_info WHERE mark>500 AND sex='男'; /*使用逻辑表达式选择行*/SELECT stu_id,stu_name,birthday,sex FROM stu_info WHERE ( mark>500 OR sex='男') AND sdept="商学院"; SELECT * FROM stu_info WHERE address IS NULL;/*NULL 空值判断*/SELECT * FROM stu_info WHERE mark BETWEEN 500 AND 650;/*限定数据范围*/SELECT * FROM stu_info WHERE sdept IN ('信息学院','商学院');/*限制检索数据的范围 离散数据范围IN关键字*/SELECT * FROM stu_info WHERE stu_name LIKE '张%';/*模糊查询 查询所有姓张的数据，NOT LIKE实现排除查询*/SELECT * FROM stu_info WHERE stu_name LIKE '张_';/*查询所有姓张的数据且姓名是两个数字*//*SELECT * FROM stu_info WHERE stu_name LIKE '[张王]%';/* 通配符在其中可能存在问题 存在bug*//*SELECT * FROM stu_info WHERE stu_name LIKE '^[张王]';/*存在bug*/SELECT * FROM stu_info WHERE sex="男"ORDER BY mark DESC,Stu_id;/*排序查找结果 ,Stu_id列名相同可以根据学号来排*/ SELECT COUNT(*) AS '学生人数' FROM stu_info;/*聚合函数 统计学生人数*//*分组筛选 加入where语句*/SELECT stu_id,MAX(grade),MIN(grade),AVG(grade),SUM(grade) FROM stu_info WHERE sex="男" GROUP BY stu_id HAVING AVG(grade)>80 ;/*使用WHERE语句实现的连接，查出课程编号为701的同学学号成绩姓名*/SELECT stu_info.stu_id,stu_name,stu_info.grade FROM stu_info,course_info WHERE stu_info.stu_id=course_info.stu_id AND course_id="701";/*连接查询分组筛选*/SELECT stu_info.stu_id,stu_name,stu_info.grade FROM stu_info,course_info WHERE stu_info.stu_id=course_info.stu_id GROUP BY stu_id HAVING grade>70;/*单列单值嵌套查询*/SELECT * FROM stu_info where birthday<(select birthday from stu_info where stu_id=111545235);/*单列多值嵌套查询 IN*/SELECT * FROM course_info WHERE stu_id IN(SELECT stu_id FROM stu_info WHERE sdept="信息学院");/*单列多只的转换连接*/SELECT * FROM stu_info,course_info WHERE stu_info.stu_id=course_info.stu_id AND sdept="信息学院";/*单列多值嵌套查询 ALL ANY*/SELECT stu_id,stu_name FROM stu_info WHERE mark<ANY(SELECT mark FROM stu_info WHERE sdept="电信学院");