关于SQL 语句常用的一些查询收藏

 create database xuesheng
 go
 use xuesheng
 go
 /*学生表*/
 create table Student
 (
    S# int identity(1,1) primary key,
    Sname varchar(50) null,
    Sage int not null,
    Ssex int not null
 )
 go
 /*教师表*/
 create table Teacher
 (
 T# int identity(1,1) primary key,
 Tname varchar(100) null
 )
 go
 /*课程表*/
 create table Course
 (
    C# int identity(1,1) primary key,
    Cname varchar(50) null,
    T# int foreign key references Teacher(T#)
 )
 go
 /*成绩表*/
 create table SC
 (
 S# int foreign key references Student(S#),
 C# int foreign key references Course(c#), /*课程表*/
 score int not null
 )
 go

 /* 查询平均成绩大于80分的同学的学号和平均成绩 */
 select S#,avg(score) from sc group by S# having avg(score) >80

 /*查询所有同学的学号、姓名、选课数、总成绩*/
 select Student.S#,Student.Sname,count(SC.C#),sum(score) from Student left Outer join SC on Student.S#=SC.S# group by Student.S#,Sname

 /*查询姓“李”的老师的个数*/
 select count(distinct(Tname)) from Teacher where Tname like '李%'

 /* 5.查询没学过“张老师”老师课的同学的学号、姓名*/
 select Student.S#,Student.Sname from Student where S# not in (select distinct( SC.S#) from SC,Course,Teacher where SC.C#=Course.C# and Teacher.T#=Course.T# and Teacher.Tname='张老师')

 /*in 的使用方法*/
 select * from Student where s# in (1)
 /**/
 select * from Student where s#=object_id('s#')
 /**/
 select * from Student where not exists (select * from sc where student.s# =sc.s#)

 /*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 from sc group by C# order by count(*) desc,c#

 /*检索至少选修两门课程的学生学号*/
 select s# from sc group by s# having count(*)>=2

 /*查询各个课程及相应的选修人数 */
 select count(*) from sc group by c#

 /*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 FROM SC t1 WHERE score IN (SELECT TOP 2 score FROM SC WHERE t1.C#= C# ORDER BY score DESC) ORDER BY t1.C#;

 /************************************************************
    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 from sc group by C# order by count(*) desc,c#

 /* 查询全部学生都选修的课程的课程号和课程名 */
 select C#,Cname from Course where C# in (select c# from sc group by c#)

 /* 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='张老师')

 /* 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 by S#;

 /* 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#=''and score <80 order by score desc;

 /* 50、删除“002”同学的“001”课程的成绩 */
 delete from Sc where S#=''and C#='';

 /* 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 from SC group by S# ) as T1
     where 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 from SC group by S#) as T2 order by 平均成绩 desc;

 /* 按各科平均成绩从低到高和及格率的百分数从高到低顺序*/
    SELECT t.C# AS 课程号,max(course.Cname)AS 课程名,isnull(AVG(score),0) AS 平均成绩,100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS 及格百分数
    FROM SC T,Course where t.C#=course.C# GROUP BY t.C# ORDER BY 100 * SUM(CASE WHEN isnull(score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC

 /* 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 AS Z where T.C#=C.C# and C.T#=Z.T# GROUP BY C.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 3
       SC.S# As 学生学号,
         Student.Sname AS 学生姓名 ,
       T1.score AS 企业管理,
       T2.score AS 马克思,
       T3.score AS UML,
       T4.score AS 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 AS T1
                       ON SC.S# = T1.S# AND T1.C# = ''
             LEFT JOIN SC AS T2
                       ON SC.S# = T2.S# AND T2.C# = ''
             LEFT JOIN SC AS T3
                       ON SC.S# = T3.S# AND T3.C# = ''
             LEFT JOIN SC AS T4
                       ON SC.S# = T4.S# AND T4.C# = ''
       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 WITH TIES
             ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0)
       FROM sc
             LEFT JOIN sc AS T1
                       ON sc.S# = T1.S# AND T1.C# = ''
             LEFT JOIN sc AS T2
                       ON sc.S# = T2.S# AND T2.C# = ''
             LEFT JOIN sc AS T3
                       ON sc.S# = T3.S# AND T3.C# = ''
             LEFT JOIN sc AS T4
                       ON sc.S# = T4.S# AND T4.C# = ''
       ORDER BY ISNULL(T1.score,0) + ISNULL(T2.score,0) + ISNULL(T3.score,0) + ISNULL(T4.score,0) DESC);

 /*、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 -]
     FROM SC,Course
     where SC.C#=Course.C#
     GROUP BY SC.C#,Cname;

 /*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 FROM SC GROUP BY S# ) AS T1
       WHERE 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
       FROM SC GROUP BY S#) AS T2 ORDER BY 平均成绩 desc;

 /* 26、查询每门课程被选修的学生数*/
     select c#,count(S#) from sc group by C#;

 /*27、查询出只选修了2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 from SC ,Student where SC.S#=Student.S# group by SC.S# ,Student.Sname having count(C#)=2;

 /*28、查询男生、女生人数*/
     Select count(Ssex) as 男生人数 from Student group by Ssex having Ssex=1
     Select count(Ssex) as 女生人数 from Student group by Ssex having Ssex=0

 /* 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)) as age from student where CONVERT(char(11),DATEPART(year,Sage))='';

 /*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) from Student,SC where Student.S#=SC.S# group by SC.S#,Sname having    avg(score)>80;

 /*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) from Student,SC,Course where SC.S#=Student.S# and SC.C#=Course.C# and Course.Cname='c#' and score <85;

 /*35、查询所有学生的选课情况；*/
     SELECT SC.S#,SC.C#,Sname,Cname FROM SC,Student,Course where 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 distinct student.S#,student.Sname,SC.C#,SC.score FROM student,Sc WHERE 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 score<60 order by C# ;

 /*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#='';

 /*39、求选了课程的学生人数 */
     select count(*) from sc;

 /*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*/
     select Student.Sname,score from Student,SC,Course C,Teacher where Student.S#=SC.S# and SC.C#=C.C# and C.T#=Teacher.T# and Teacher.Tname='张老师' 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 by C#;

 /*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# ;

 alter table [sc] alter column score int not null;
 alter table [Student] alter column Sage int null; /*修改字段*/
 alter table [Student] alter column Ssex int null
 alter table [dbo].[Student] add Sage int null /*添加字段*/
 alter table [dbo].[Student] add Ssex int null

 insert into Student values('党清华',20,1)
 insert into Student values('张三',25,0)
 insert into Student values('李四',23,1)
 insert into Student values('王五',28,0)

 insert into Teacher values('张老师')
 insert into Teacher values('李老师')
 insert into Teacher values('王老师')

 insert into Course values('c++',1)
 insert into Course values('C#',2)
 insert into Course values('asp.net',3)

 insert into SC values(1,1,80)
 insert into SC values(2,2,85)
 insert into SC values(3,3,80)

 select * from Student
 select * from Teacher
 select * from Course
 select * from SC