数据库MySQL查询设计||给定四个关联表，其定义和数据加载如下：-- 学生表 Student-- 选课表 SC

news2024/9/8 23:46:51

SQL查询设计

给定四个关联表，其定义和数据加载如下：

-- 学生表 Student

create table Student(Sno varchar(6), Sname varchar(10), Sdate datetime, Ssex varchar(10));

insert into Student values('01' , '赵雷' , '1999-01-01' , '男');

insert into Student values('02' , '钱电' , '1999-12-21' , '男');

insert into Student values('03' , '孙风' , '1999-05-20' , '男');

insert into Student values('04' , '李云' , '1999-08-06' , '男');

insert into Student values('05' , '周梅' , '2000-12-01' , '女');

insert into Student values('06' , '吴兰' , '2001-03-01' , '女');

insert into Student values('07' , '郑竹' , '1998-07-01' , '女');

insert into Student values('08' , '王菊' , '1999-01-20' , '女');

-- 选课表 SC

create table SC(Sno varchar(10), Cno varchar(10), score decimal(18,1));

insert into SC values('01' , '01' , 80);

insert into SC values('01' , '02' , 90);

insert into SC values('01' , '03' , 99);

insert into SC values('02' , '01' , 70);

insert into SC values('02' , '02' , 60);

insert into SC values('02' , '03' , 80);

insert into SC values('03' , '01' , 80);

insert into SC values('03' , '02' , 80);

insert into SC values('03' , '03' , 80);

insert into SC values('04' , '01' , 50);

insert into SC values('04' , '02' , 30);

insert into SC values('04' , '03' , 20);

insert into SC values('05' , '01' , 76);

insert into SC values('05' , '02' , 87);

insert into SC values('06' , '01' , 31);

insert into SC values('06' , '03' , 34);

insert into SC values('07' , '02' , 89);

insert into SC values('07' , '03' , 98);

-- 课程表 Course

create table Course(Cno varchar(10),Cname varchar(10),Tno varchar(10));

insert into Course values('01' , '语文' , '02');

insert into Course values('02' , '数学' , '01');

insert into Course values('03' , '英语' , '03');

-- 教师表 Teacher

create table Teacher(Tno varchar(10),Tname varchar(10));

insert into Teacher values('01' , '张三');

insert into Teacher values('02' , '李四');

insert into Teacher values('03' , '王五');

insert into Teacher values('04' , '张小五');

试按以下操作要求完成SQL语言设计。

1.查询「张」姓老师的数量。

select tname,count(tno)as '数量' from teacher group by tno having tname like'%张%';

SELECT COUNT(1) AS counts FROM Teacher WHERE TName LIKE '%张%';

2.查询平均成绩大于等于 80 分的学生信息，输出其编号Sno、姓名Sname和平均成绩Avg_score三列内容。

SELECT t1.Sno,t1.Sname,t2.Avg_score

FROM Student AS t1

INNER JOIN (SELECT Sno,AVG(score) AS Avg_score FROM SC GROUP BY Sno

HAVING AVG(score)>=80) AS t2 ON t1.Sno=t2.Sno

3.查询Student表中所有同学的学生编号Sno、学生姓名Sname和对应选课总数、所有课程的总成绩(没有成绩的显示为 null )。

SELECT t1.Sno,t1.Sname,COUNT(t2.Cno) AS CountCno,SUM(t2.score) AS score

FROM Student AS t1

LEFT JOIN SC AS t2 ON t1.Sno=t2.Sno

GROUP BY t1.Sno,t1.Sname

4.查询选课表SC内没有选修课程表Course里所列所有课程的学生信息，输出其Sno、Sname、Sdate和Ssex四列内容。

SELECT t3.*,t4.*

FROM (

SELECT t1.Sno,t1.Sname,t1.Sdate,t1.Ssex,t2.Cno,t2.Cname

FROM Student AS t1

LEFT JOIN Course AS t2 ON 1=1

) AS t3

LEFT JOIN SC AS t4 ON t3.Sno=t4.Sno AND t3.Cno=t4.Cno

WHERE t4.Sno IS NULL

5.查询和" 01 "号学生学习的课程完全相同的其他学生信息，输出其学号Sno内容。

select sc.Sno from sc as sc

where Sno in

(select distinct sc.Sno from sc

where Sno<>'01'

and Cno in(select distinct Cno from sc where Sno='01')

group by Sno

having

count(1)=(select count(1) from sc where Sno='01'))

group by Sno

having count(1)=(select count(sc.Sno) from sc as sc where sc.Sno='01')

6. 查询没有学过"张三"老师讲授的任一门课程的学生姓名。

SELECT t1.Sno,t1.Sname

FROM Student AS t1

LEFT JOIN (

SELECT DISTINCT Sno FROM SC WHERE Cno NOT IN (SELECT Cno FROM Course WHERE Tno IN (SELECT Tno FROM Teacher WHERE Tname='张三'))

) AS t2 ON t1.Sno=t2.Sno

7.编程
向Course中添加新课（课号和课名）时，第三个Tno教师号字段值自动填入对应SC表中按教师分类成绩平均分最高的教师编号。
请测试追加新课程“04，数据库”的效果。(切记：测试操作请放在最后进行！！！)

create trigger trigg
on Course
after insert
as
    declare @topTno varchar(20);

	SELECT @topTno=t3.Tno
	FROM
	(
	SELECT t2.Tno,AVG(t1.score) AS AvgScore
	FROM SC AS t1
	LEFT JOIN Course AS t2 ON t1.Cno=t2.Cno
	GROUP BY t2.Tno
	) AS t3
	ORDER BY t3.AvgScore DESC limit 0,1

	UPDATE Course SET Tno=@topTno WHERE Tno in (select Tno from inserted)
GO

INSERT INTO Course(Cno,Cname) VALUES ('04','数据库')