mysql的四表联查_数据库四表联查

待我称王封你为后i 2022-10-28 13:24 215阅读 0赞

21、查询不同老师所教不同课程平均分从高到低显示SELECT max(Z.T\#) AS 教师ID,MAX(Z.Tname) AS 教师姓名,C.C\# AS 课程ＩＤ,MAX(C.Cname) AS 课程名称,AVG(Score) AS平均成绩FROM SC AS T,Course AS C ,Teacher ASZwhere T.C\#=C.C\# and C.T\#=Z.T\#GROUP BYC.C\#ORDER BY AVG(Score) DESC

22、查询如下课程成绩第 3 名到第 6 名的学生成绩单：企业管理(001)，马克思(002)，UML (003)，数据库(004)\[学生ID\],\[学生姓名\],企业管理,马克思,UML,数据库,平均成绩SELECT DISTINCT top 3SC.S\#As学生学号,

Student.SnameAS学生姓名 ,

T1.scoreAS企业管理,

T2.scoreAS马克思,

T3.scoreASUML,

T4.scoreAS数据库,ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) as总分FROM Student,SC LEFT JOIN SC AST1ON SC.S\# = T1.S\# AND T1.C\# = '001'

LEFT JOIN SC AST2ON SC.S\# = T2.S\# AND T2.C\# = '002'

LEFT JOIN SC AST3ON SC.S\# = T3.S\# AND T3.C\# = '003'

LEFT JOIN SC AST4ON SC.S\# = T4.S\# AND T4.C\# = '004'

WHERE student.S\#=SC.S\# and

ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)NOT IN(SELECT

DISTINCT

TOP 15 WITHTIESISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)FROMscLEFT JOIN sc AST1ON sc.S\# = T1.S\# AND T1.C\# = 'k1'

LEFT JOIN sc AST2ON sc.S\# = T2.S\# AND T2.C\# = 'k2'

LEFT JOIN sc AST3ON sc.S\# = T3.S\# AND T3.C\# = 'k3'

LEFT JOIN sc AST4ON sc.S\# = T4.S\# AND T4.C\# = 'k4'

ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) DESC);23、统计列印各科成绩,各分数段人数:课程ID,课程名称,\[100-85\],\[85-70\],\[70-60\],\[<60\]

SELECT SC.C\# as 课程ID, Cname as课程名称

,SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS \[100 - 85\],SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS \[85 - 70\],SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS \[70 - 60\],SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) AS \[60 -\]

FROMSC,Coursewhere SC.C\#=Course.C\#GROUP BYSC.C\#,Cname;24、查询学生平均成绩及其名次SELECT 1+(SELECT COUNT( distinct平均成绩)FROM (SELECT S\#,AVG(score) AS平均成绩FROMSCGROUP BYS\#

)AST1WHERE 平均成绩 > T2.平均成绩) as名次,

S\#as学生学号,平均成绩FROM (SELECT S\#,AVG(score) 平均成绩FROMSCGROUP BYS\#

)AST2ORDER BY 平均成绩 desc;25、查询各科成绩前三名的记录:(不考虑成绩并列情况)SELECT t1.S\# as 学生ID,t1.C\# as 课程ID,Score as分数FROMSC t1WHERE score IN (SELECT TOP 3scoreFROMSCWHERE t1.C\#=C\#ORDER BY score DESC)ORDER BYt1.C\#;26、查询每门课程被选修的学生数select c\#,count(S\#) from sc group byC\#;27、查询出只选修了一门课程的全部学生的学号和姓名select SC.S\#,Student.Sname,count(C\#) AS选课数fromSC ,Studentwhere SC.S\#=Student.S\# group by SC.S\# ,Student.Sname having count(C\#)=1;28、查询男生、女生人数Select count(Ssex) as 男生人数 from Student group by Ssex having Ssex='男';Select count(Ssex) as 女生人数 from Student group by Ssex having Ssex='女'；29、查询姓“张”的学生名单SELECT Sname FROM Student WHERE Sname like '张%';30、查询同名同性学生名单，并统计同名人数select Sname,count(\*) from Student group by Sname having count(\*)>1;;31、1981年出生的学生名单(注：Student表中Sage列的类型是datetime)select Sname, CONVERT(char (11),DATEPART(year,Sage)) asagefromstudentwhere CONVERT(char(11),DATEPART(year,Sage))='1981';32、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列Select C\#,Avg(score) from SC group by C\# order by Avg(score),C\# DESC;33、查询平均成绩大于85的所有学生的学号、姓名和平均成绩select Sname,SC.S\# ,avg(score)fromStudent,SCwhere Student.S\#=SC.S\# group by SC.S\#,Sname having avg(score)>85;34、查询课程名称为“数据库”，且分数低于60的学生姓名和分数Select Sname,isnull(score,0)fromStudent,SC,Coursewhere SC.S\#=Student.S\# and SC.C\#=Course.C\# and Course.Cname='数据库'and score <60;35、查询所有学生的选课情况；SELECTSC.S\#,SC.C\#,Sname,CnameFROMSC,Student,Coursewhere SC.S\#=Student.S\# and SC.C\#=Course.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 distinctstudent.S\#,student.Sname,SC.C\#,SC.scoreFROMstudent,ScWHERE SC.score>=70 AND SC.S\#=student.S\#;37、查询不及格的课程，并按课程号从大到小排列select c\# from sc where scor e <60 order byC\# ;38、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；select SC.S\#,Student.Sname from SC,Student where SC.S\#=Student.S\# and Score>80 and C\#='003';39、求选了课程的学生人数select count(\*) fromsc;40、查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩selectStudent.Sname,scorefromStudent,SC,Course C,Teacherwhere Student.S\#=SC.S\# and SC.C\#=C.C\# and C.T\#=Teacher.T\# and Teacher.Tname='叶平' and SC.score=(select max(score)from SC where C\#=C.C\# );41、查询各个课程及相应的选修人数select count(\*) from sc group byC\#;42、查询不同课程成绩相同的学生的学号、课程号、学生成绩select distinct A.S\#,B.score from SC A ,SC B where A.Score=B.Score and A.C\# <>B.C\# ;43、查询每门功成绩最好的前两名SELECT t1.S\# as 学生ID,t1.C\# as 课程ID,Score as分数FROMSC t1WHERE score IN (SELECT TOP 2scoreFROMSCWHERE t1.C\#=C\#ORDER BY score DESC)ORDER BYt1.C\#;44、统计每门课程的学生选修人数(超过10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，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 C\# as 课程号,count(\*) as人数fromscgroup byC\#order by count(\*) desc,c\#45、检索至少选修两门课程的学生学号selectS\#fromscgroup bys\#having count(\*) > = 2

46、查询全部学生都选修的课程的课程号和课程名selectC\#,CnamefromCoursewhere C\# in (select c\# from sc group byc\#)47、查询没学过“叶平”老师讲授的任一门课程的学生姓名select Sname from Student where S\# not in (select S\# from Course,Teacher,SC where Course.T\#=Teacher.T\# and SC.C\#=course.C\# and Tname='叶平');48、查询两门以上不及格课程的同学的学号及其平均成绩select S\#,avg(isnull(score,0)) from SC where S\# in (select S\# from SC where score <60 group by S\# having count(\*)>2)group byS\#;49、检索“004”课程分数小于60，按分数降序排列的同学学号select S\# from SC where C\#='004'and score <60 order by score desc;50、删除“002”同学的“001”课程的成绩delete from Sc where S\#='001'and C\#='001';