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--1.学生表Student(S,Sname,Sage,Ssex) --S 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别--2.课程表 Course(C,Cname,T) --C --课程编号,Cname 课程名称,T 教师编号--3.教师表 Teacher(T,Tname) --T 教师编号,Tname 教师姓名--4.成绩表 SC(S,C,score) --S 学生编号,C 课程编号,score 分数*/--创建测试数据create table Student(S varchar(10),Sname varchar(10),Sage datetime,Ssex nvarchar(10))insert into Student values('01' , '赵雷' , '1990-01-01' , '男')insert into Student values('02' , '钱电' , '1990-12-21' , '男')insert into Student values('03' , '孙风' , '1990-05-20' , '男')insert into Student values('04' , '李云' , '1990-08-06' , '男')insert into Student values('05' , '周梅' , '1991-12-01' , '女')insert into Student values('06' , '吴兰' , '1992-03-01' , '女')insert into Student values('07' , '郑竹' , '1989-07-01' , '女')insert into Student values('08' , '王菊' , '1990-01-20' , '女')create table Course(C varchar(10),Cname,varchar(10),T 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')create table Teacher(T 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')create table SC(S varchar(10),C 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)mysql...--1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数SELECT a.*,b.score AS'01分数',c.score AS '02分数'FROM student aINNER JOIN sc bON a.s=b.s AND b.c='01'INNER JOIN sc cON a.s=c.s AND c.c='02'WHERE b.score>c.score--2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数--3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩SELECT a.s       ,a.sname       ,AVG(b.score) AS avgnumFROM student aINNER JOIN sc bON a.s=b.sGROUP BY a.s       ,a.snameHAVING AVG(b.score)>60--4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩--5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩SELECT a.s       ,a.sname       ,COUNT(b.c)       ,SUM(b.score)FROM student aLEFT JOIN sc bON a.s=b.sGROUP BY 1,2--6、查询"李"姓老师的数量 SELECT COUNT(1) FROM teacher WHERE tname LIKE '李%'--7、查询学过"张三"老师授课的同学的信息 SELECT a.*FROM student aINNER JOIN sc bON a.s=b.sINNER JOIN course cON b.c=c.cINNER JOIN teacher dON c.t=d.tWHERE d.tname='张三'GROUP BY 1,2,3,4--方法2SELECT a.*FROM student aLEFT JOIN (	SELECT a.*	FROM student a	INNER JOIN sc b	ON a.s=b.s	INNER JOIN course c	ON b.c=c.c	INNER JOIN teacher d	ON c.t=d.t	WHERE d.tname='张三'	GROUP BY 1,2,3,4)bON a.s=b.sWHERE b.s IS NULL--8、查询没学过"张三"老师授课的同学的信息 SELECT a.*FROM student aLEFT JOIN sc bON a.s=b.s						//找出所有学生学的课WHERE NOT EXISTS(		SELECT * 		FROM course aa		INNER JOIN teacher b		ON aa.t=b.t		INNER JOIN sc c		ON aa.c=c.c					//找出所有张三老师教的课		WHERE b.tname='张三'		AND c.s=a.s	)GROUP BY 1,2,3,4我的答案：SELECTstu.*FROMstudent stuWHERE stu.s NOT IN(SELECTs.sFROMteacher t INNER JOIN course c ON t.T=c.t_id INNER JOIN sc s ON c.id=s.c WHERE t.Tname='张三')--9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息SELECT a.*FROM student aINNER JOIN sc b				//找出所有学过01课程的学生ON a.s=b.s AND b.c='01'INNER JOIN sc cON a.s=c.s AND c.c='02'		//在01的基础上找出所有学过02基础的学生--10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息select *from student aleft join sc b			//左链接的作用是使左表为一张大表，使得右表没匹配的字段为空on a.s=b.s and b.c='01'   //学过01课程的学生left join sc con a.s=c.s and c.c='02'   //学过02课程的学生where b.c='01' and c.c is null    //因为左链接的缘故，没学过02的学生结果为空方法二：SELECT a1.*,b.cFROM student a1INNER JOIN sc bON a1.s=b.s AND b.c='01'    //所有学过01课程的学生WHERE NOT EXISTS(SELECT a2.*,b.cFROM student a2INNER JOIN sc bON a2.s=b.s AND b.c='01'INNER JOIN sc cON a2.s=c.s AND c.c='02'		//学过01和02的学生WHERE a1.s=a2.s)--11、查询没有学全所有课程的同学的信息 SELECT a.*FROM student aLEFT JOIN sc bON a.s=b.sLEFT JOIN (SELECT COUNT(1) anum FROM course) cON 1=1GROUP BY 1,2,3,4HAVING MAX(c.anum)>COUNT(b.c)方法二：SELECT(CASE WHEN (IFNULL(tab1.c1,0)+IFNULL(tab1.c2,0)+IFNULL(tab1.c3,0))!=06 THEN tab1.p END) qname,(CASE WHEN (IFNULL(tab1.c1,0)+IFNULL(tab1.c2,0)+IFNULL(tab1.c3,0))!=06 THEN tab1.ename END) ssFROM(SELECT a.S p,a.Sname ename,b.c c1,c.c c2,d.c c3FROM student aLEFT JOIN sc bON a.s=b.s AND b.c='01'LEFT JOIN sc cON a.s=c.s AND c.c='02'LEFT JOIN sc dON a.s=d.s AND d.c='03') tab1GROUP BY qnameHAVING IFNULL(qname,0)!=0--12、查询至少有一门课与学号为"01"的同学所学相同的同学的信息 SELECT a.*FROM student aINNER JOIN sc bON a.s=b.sWHERE EXISTS(    SELECT 1 FROM sc WHERE s='01' AND c=b.c)GROUP BY 1,2,3,4--13、查询和"01"号的同学学习的课程完全相同的其他同学的信息 SELECT a.s,a.sname,a.sage,a.ssexFROM (SELECT a.*,COUNT(b.c) AS snum	FROM student a	INNER JOIN sc b	ON a.s=b.s	WHERE EXISTS(	    SELECT 1 FROM sc WHERE s='01' AND c=b.c	)	GROUP BY 1,2,3,4)aINNER JOIN (SELECT a.*,COUNT(b.c) AS anum	FROM student a	INNER JOIN sc b	ON a.s=b.s	GROUP BY 1,2,3,4)bON a.s=b.sINNER JOIN (SELECT COUNT(1) AS num1 FROM sc WHERE s='01')cON 1=1WHERE a.snum=b.anum AND a.snum=c.num1--方法二SELECT a.*	,COUNT(b.c) AS anum	,SUM(CASE WHEN EXISTS(SELECT 1 FROM sc WHERE s='01' AND c=b.c) THEN 1 ELSE 0 END) AS snum	,MAX(c.num1) AS num1FROM student aINNER JOIN sc bON a.s=b.sINNER JOIN (SELECT COUNT(1) AS num1 FROM sc WHERE s='01')cON 1=1GROUP BY 1,2,3,4HAVING anum=snum AND anum=num1--14、查询没学过"张三"老师讲授的任一门课程的学生姓名 SELECT a.*FROM student aLEFT JOIN(	SELECT a.s	FROM student a	LEFT JOIN sc b	ON a.s=b.s	LEFT JOIN course c	ON b.c=c.c	LEFT JOIN teacher d	ON c.t=d.t AND d.tname='张三'	WHERE d.t IS NOT NULL	)bON a.s=b.sWHERE b.s IS NULL--15、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩 SELECT a.s       ,a.sname       ,AVG(b.score)FROM student aINNER JOIN sc bON a.s=b.sGROUP BY 1,2HAVING SUM(CASE WHEN b.score>=60 THEN 0 ELSE 1 END)>=2--16、检索"01"课程分数小于60，按分数降序排列的学生信息SELECT a.*       ,b.scoreFROM student aINNER JOIN sc bON a.s=b.sWHERE   b.c='01'  AND b.score<60ORDER BY b.score DESC--17、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩SELECT a.*       ,SUM(CASE WHEN b.c='01' THEN b.score ELSE 0 END) AS s01       ,SUM(CASE WHEN b.c='02' THEN b.score ELSE 0 END) AS s02       ,SUM(CASE WHEN b.c='03' THEN b.score ELSE 0 END) AS s03       ,AVG(CASE WHEN b.score IS NULL THEN 0 ELSE b.score END) avsFROM student aLEFT JOIN sc bON a.s=b.sGROUP BY 1,2,3,4ORDER BY avs DESC方法二：SELECTtab2.*,avge.avFROM(SELECT					//行列转换（没修的课程列为空，再相加）tab1.s s,SUM(c1),SUM(c2),SUM(c3)FROM(SELECTstu.s s,(CASE WHEN s.c='01' THEN s.c END)c1,(CASE WHEN s.c='02' THEN s.c END)c2,(CASE WHEN s.c='03' THEN s.c END)c3FROMstudent stuINNER JOIN sc s ON stu.s=s.s)tab1GROUP BY tab1.s)tab2INNER JOIN(SELECTAVG(score) av,s stuFROMscGROUP BY s) avgeON avge.stu=tab2.s--18、查询各科成绩最高分、最低分和平均分：以如下形式显示：课程ID，课程name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率--及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90SELECT a.c       ,a.cname       ,MAX(b.score)       ,MIN(b.score)       ,AVG(b.score)       ,SUM(CASE WHEN b.score>=60 THEN 1 ELSE 0 END)/COUNT(1)       ,SUM(CASE WHEN b.score>=70 AND b.score<80 THEN 1 ELSE 0 END)/COUNT(1)       ,SUM(CASE WHEN b.score>=80 AND b.score<90 THEN 1 ELSE 0 END)/COUNT(1)       ,SUM(CASE WHEN b.score>=90 THEN 1 ELSE 0 END)/COUNT(1)FROM course aINNER JOIN sc bON a.c=b.cGROUP BY 1,2--19、按各科成绩进行排序，并显示排名SET @rn:=0;SELECT a.*,@rn:=@rn+1FROM(    SELECT a.*,b.score    FROM course a    INNER JOIN sc b    ON a.c=b.c    WHERE a.c='01'    ORDER BY b.c,score DESC)a方法二：SELECTtab1.*,(COUNT(*))rangFROM//排名，自连接，名次取决于分数大于自己的人数(SELECT a.c c1,a.cname c2,b.s s1,b.score s2    FROM course a    INNER JOIN sc b    ON a.c=b.c    WHERE a.c='01'    ORDER BY b.c,score DESC)tab1    INNER JOIN(SELECT a.c c1,a.cname c2,b.s s1,b.score s2    FROM course a    INNER JOIN sc b    ON a.c=b.c    WHERE a.c='01'    ORDER BY b.c,score DESC)tab2    ON tab1.s1!=tab2.s1      WHERE tab1.s2<=tab2.s2    GROUP BY tab1.s1ORDER BY rang--20、查询学生的总成绩并进行排名SELECT a.*       ,COUNT(b.c)+1 asallFROM sc aLEFT JOIN sc bON a.c=b.c AND a.score
   
    85 THEN 1 ELSE 0 END) AS '[100-85]'       ,SUM(CASE WHEN b.score<=85 AND b.score>70 THEN 1 ELSE 0 END) AS '[85-70]'       ,SUM(CASE WHEN b.score<=70 AND b.score>60 THEN 1 ELSE 0 END) AS '[70-60]'       ,SUM(CASE WHEN b.score<=60 AND b.score>0 THEN 1 ELSE 0 END) AS '[60-0]'       ,SUM(CASE WHEN b.score<=100 AND b.score>85 THEN 1 ELSE 0 END)/COUNT(1) AS '[100-85]%'       ,SUM(CASE WHEN b.score<=85 AND b.score>70 THEN 1 ELSE 0 END)/COUNT(1) AS '[85-70]%'       ,SUM(CASE WHEN b.score<=70 AND b.score>60 THEN 1 ELSE 0 END)/COUNT(1) AS '[70-60]%'       ,SUM(CASE WHEN b.score<=60 AND b.score>0 THEN 1 ELSE 0 END)/COUNT(1) AS '[60-0]%'FROM course aINNER JOIN sc bON a.c=b.cGROUP BY 1,2--24、查询学生平均成绩及其名次 SELECT a.*       ,COUNT(b.s)+1FROM (	SELECT a.*,AVG(CASE WHEN b.score IS NULL THEN 0 ELSE b.score END) AS ascore	FROM student a	LEFT JOIN sc b	ON a.s=b.s	GROUP BY 1,2,3,4      )aLEFT JOIN(	SELECT a.*,AVG(CASE WHEN b.score IS NULL THEN 0 ELSE b.score END) AS ascore	FROM student a	LEFT JOIN sc b	ON a.s=b.s	GROUP BY 1,2,3,4      )bON a.ascore
    
     1--31、查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime) SELECT * FROM student WHERE YEAR(sage)=1990--32、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号SELECT a.*       ,AVG(b.score) ascoreFROM course aLEFT JOIN sc bON a.c=b.cGROUP BY 1,2,3ORDER BY ascore DESC,a.c--33、查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩 SELECT a.*       ,AVG(b.score) ascoreFROM student aLEFT JOIN sc bON a.s=b.sGROUP BY 1,2,3,4HAVING ascore>=85--34、查询课程名称为"数学"，且分数低于60的学生姓名和分数 SELECT c.*FROM course aLEFT JOIN sc bON a.c=b.cLEFT JOIN student cON b.s=c.sWHERE a.cname='数学'AND b.score<60--35、查询所有学生的课程及分数情况； SELECT *FROM sc aINNER JOIN student bON a.s=b.sINNER JOIN course cON a.c=c.c--36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数； SELECT b.sname       ,c.cname       ,a.scoreFROM sc aINNER JOIN student bON a.s=b.sINNER JOIN course cON a.c=c.cWHERE a.score>70--37、查询不及格的课程--38、查询课程编号为01且课程成绩在80分以上的学生的学号和姓名； SELECT a.*FROM student aINNER JOIN sc bON a.s=b.sWHERE b.c='01' AND b.score>80--39、求每门课程的学生人数 --40、查询选修"张三"老师所授课程的学生中，成绩最高的学生信息及其成绩SELECT a.*,b.scoreFROM student aINNER JOIN sc bON a.s=b.sINNER JOIN(	SELECT c.c	       ,MAX(c.score) AS maxscore	FROM teacher a	INNER JOIN course b	ON a.t=b.t	INNER JOIN sc c	ON b.c=c.c	WHERE a.tname='张三'	GROUP BY c)cON b.c=c.c AND b.score=c.maxscore--41、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩 SELECT a.s       ,a.c       ,a.scoreFROM sc aINNER JOIN (	SELECT a.score	       ,b.s	       ,COUNT(1)	FROM sc a	INNER JOIN student b	ON a.s=b.s	GROUP BY a.score,b.s	HAVING COUNT(1)>1)bON a.s=b.s AND a.score=b.score方法二SELECT a.*FROM sc aLEFT JOIN sc bON a.s=b.s AND a.score=b.score AND a.c<>b.cGROUP BY 1,2,3HAVING COUNT(b.s)>0--42、查询每门功成绩最好的前两名 --43、统计每门课程的学生选修人数（超过5人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列  SELECT a.c       ,COUNT(1) AS pnumFROM sc aGROUP BY 1HAVING pnum>5ORDER BY pnum DESC,a.c--44、检索至少选修两门课程的学生学号 --45、查询选修了全部课程的学生信息 --46、查询各学生的年龄SELECT a.*,YEAR(CURDATE())-YEAR(a.sage)FROM student a--47、查询本周过生日的学生SELECT a.*FROM student aWHERE CONCAT(MONTH(a.sage),DAY(a.sage))>=CONCAT(MONTH(SUBDATE(CURDATE(),WEEKDAY(CURDATE()))),DAY(SUBDATE(CURDATE(),WEEKDAY(CURDATE()))))AND CONCAT(MONTH(a.sage),DAY(a.sage))<=CONCAT(MONTH(SUBDATE(CURDATE(),WEEKDAY(CURDATE())-6)),DAY(SUBDATE(CURDATE(),WEEKDAY(CURDATE())-6)))--48、查询下周过生日的学生--49、查询本月过生日的学生SELECT a.* FROM student a WHERE MONTH(a.sage)=MONTH(CURDATE())--50、查询下月过生日的学生SELECT a.* FROM student a WHERE MONTH(a.sage)=MONTH(CURDATE())+1
    
   

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