SQL 多表查詢 50例

/* 標題：一個項目涉及到的50個Sql語句(整理版) 

問題及描述： --1.學生表 Student(S#,Sname,Sage,Ssex) --S# 學生編號,Sname 學生姓名,Sage 出生年月,Ssex 學生性別 --2.課程表 Course(C#,Cname,T#) --C# --課程編號,Cname 課程名稱,T# 教師編號 --3.教師表 Teacher(T#,Tname) --T# 教師編號,Tname 教師姓名 --4.成績表 SC(S#,C#,score) --S# 學生編號,C# 課程編號,score 分數 */ --建立測試數據 create table Student(S# varchar(10),Sname nvarchar(10),Sage datetime,Ssex nvarchar(10)) insert into Student values('01' , N'趙雷' , '1990-01-01' , N'男') insert into Student values('02' , N'錢電' , '1990-12-21' , N'男') insert into Student values('03' , N'孫風' , '1990-05-20' , N'男') insert into Student values('04' , N'李雲' , '1990-08-06' , N'男') insert into Student values('05' , N'周梅' , '1991-12-01' , N'女') insert into Student values('06' , N'吳蘭' , '1992-03-01' , N'女') insert into Student values('07' , N'鄭竹' , '1989-07-01' , N'女') insert into Student values('08' , N'王菊' , '1990-01-20' , N'女') create table Course(C# varchar(10),Cname nvarchar(10),T# varchar(10)) insert into Course values('01' , N'語文' , '02') insert into Course values('02' , N'數學' , '01') insert into Course values('03' , N'英語' , '03') create table Teacher(T# varchar(10),Tname nvarchar(10)) insert into Teacher values('01' , N'張三') insert into Teacher values('02' , N'李四') insert into Teacher values('03' , N'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) go

--一、查詢"01"課程比"02"課程成績高的學生的信息及課程分數 --1.一、查詢同時存在"01"課程和"02"課程的狀況 select a.* , b.score [課程'01'的分數],c.score [課程'02'的分數] from Student a , SC b , SC c
where a.S# = b.S# and a.S# = c.S# and b.C# = '01' and c.C# = '02' and b.score > c.score --1.二、查詢同時存在"01"課程和"02"課程的狀況和存在"01"課程但可能不存在"02"課程的狀況(不存在時顯示爲null)(如下存在相同內容時再也不解釋) select a.* , b.score [課程"01"的分數],c.score [課程"02"的分數] from Student a left join SC b on a.S# = b.S# and b.C# = '01' left join SC c on a.S# = c.S# and c.C# = '02' where b.score > isnull(c.score,0)

--二、查詢"01"課程比"02"課程成績低的學生的信息及課程分數 --2.一、查詢同時存在"01"課程和"02"課程的狀況 select a.* , b.score [課程'01'的分數],c.score [課程'02'的分數] from Student a , SC b , SC c
where a.S# = b.S# and a.S# = c.S# and b.C# = '01' and c.C# = '02' and b.score < c.score --2.二、查詢同時存在"01"課程和"02"課程的狀況和不存在"01"課程但存在"02"課程的狀況 select a.* , b.score [課程"01"的分數],c.score [課程"02"的分數] from Student a left join SC b on a.S# = b.S# and b.C# = '01' left join SC c on a.S# = c.S# and c.C# = '02' where isnull(b.score,0) < c.score

--三、查詢平均成績大於等於60分的同窗的學生編號和學生姓名和平均成績 select a.S# , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.S# = b.S# group by a.S# , a.Sname having cast(avg(b.score) as decimal(18,2)) >= 60 order by a.S#

--四、查詢平均成績小於60分的同窗的學生編號和學生姓名和平均成績 --4.一、查詢在sc表存在成績的學生信息的SQL語句。 select a.S# , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.S# = b.S# group by a.S# , a.Sname having cast(avg(b.score) as decimal(18,2)) < 60 order by a.S# --4.二、查詢在sc表中不存在成績的學生信息的SQL語句。 select a.S# , a.Sname , isnull(cast(avg(b.score) as decimal(18,2)),0) avg_score from Student a left join sc b on a.S# = b.S# group by a.S# , a.Sname having isnull(cast(avg(b.score) as decimal(18,2)),0) < 60 order by a.S#

--五、查詢全部同窗的學生編號、學生姓名、選課總數、全部課程的總成績 --5.一、查詢全部有成績的SQL。 select a.S# [學生編號], a.Sname [學生姓名], count(b.C#) 選課總數, sum(score) [全部課程的總成績] from Student a , SC b where a.S# = b.S# group by a.S#,a.Sname order by a.S# --5.二、查詢全部(包括有成績和無成績)的SQL。 select a.S# [學生編號], a.Sname [學生姓名], count(b.C#) 選課總數, sum(score) [全部課程的總成績] from Student a left join SC b on a.S# = b.S# group by a.S#,a.Sname order by a.S#

--六、查詢"李"姓老師的數量 --方法1 select count(Tname) ["李"姓老師的數量] from Teacher where Tname like N'李%' --方法2 select count(Tname) ["李"姓老師的數量] from Teacher where left(Tname,1) = N'李' /* "李"姓老師的數量   ----------- 1 */

--七、查詢學過"張三"老師授課的同窗的信息 select distinct Student.* from Student , SC , Course , Teacher where Student.S# = SC.S# and SC.C# = Course.C# and Course.T# = Teacher.T# and Teacher.Tname = N'張三' order by Student.S#

--八、查詢沒學過"張三"老師授課的同窗的信息 select m.* from Student m where S# not in (select distinct SC.S# from SC , Course , Teacher where SC.C# = Course.C# and Course.T# = Teacher.T# and Teacher.Tname = N'張三') order by m.S#

--九、查詢學過編號爲"01"而且也學過編號爲"02"的課程的同窗的信息 --方法1 select Student.* from Student , SC where Student.S# = SC.S# and SC.C# = '01' and exists (Select 1 from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# = '02') order by Student.S# --方法2 select Student.* from Student , SC where Student.S# = SC.S# and SC.C# = '02' and exists (Select 1 from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# = '01') order by Student.S# --方法3 select m.* from Student m where S# in (   select S# from   (     select distinct S# from SC where C# = '01'     union all     select distinct S# from SC where C# = '02'   ) t group by S# having count(1) = 2 ) order by m.S#

--十、查詢學過編號爲"01"可是沒有學過編號爲"02"的課程的同窗的信息 --方法1 select Student.* from Student , SC where Student.S# = SC.S# and SC.C# = '01' and not exists (Select 1 from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# = '02') order by Student.S# --方法2 select Student.* from Student , SC where Student.S# = SC.S# and SC.C# = '01' and Student.S# not in (Select SC_2.S# from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# = '02') order by Student.S#

--十一、查詢沒有學全全部課程的同窗的信息 --11.一、 select Student.* from Student , SC
where Student.S# = SC.S# group by Student.S# , Student.Sname , Student.Sage , Student.Ssex having count(C#) < (select count(C#) from Course)
--11.2 select Student.* from Student left join SC on Student.S# = SC.S# group by Student.S# , Student.Sname , Student.Sage , Student.Ssex having count(C#) < (select count(C#) from Course)

--十二、查詢至少有一門課與學號爲"01"的同窗所學相同的同窗的信息 select distinct Student.* from Student , SC where Student.S# = SC.S# and SC.C# in (select C# from SC where S# = '01') and Student.S# <> '01'

--1三、查詢和"01"號的同窗學習的課程徹底相同的其餘同窗的信息 select Student.* from Student where S# in (select distinct SC.S# from SC where S# <> '01' and SC.C# in (select distinct C# from SC where S# = '01') group by SC.S# having count(1) = (select count(1) from SC where S#='01'))

--1四、查詢沒學過"張三"老師講授的任一門課程的學生姓名 select student.* from student where student.S# not in (select distinct sc.S# from sc , course , teacher where sc.C# = course.C# and course.T# = teacher.T# and teacher.tname = N'張三') order by student.S#

--1五、查詢兩門及其以上不及格課程的同窗的學號，姓名及其平均成績 select student.S# , student.sname , cast(avg(score) as decimal(18,2)) avg_score from student , sc where student.S# = SC.S# and student.S# in (select S# from SC where score < 60 group by S# having count(1) >= 2) group by student.S# , student.sname

--1六、檢索"01"課程分數小於60，按分數降序排列的學生信息 select student.* , sc.C# , sc.score from student , sc where student.S# = SC.S# and sc.score < 60 and sc.C# = '01' order by sc.score desc 

--1七、按平均成績從高到低顯示全部學生的全部課程的成績以及平均成績 --17.1 SQL 2000 靜態 select a.S# 學生編號 , a.Sname 學生姓名 ,        max(case c.Cname when N'語文' then b.score else null end) [語文],        max(case c.Cname when N'數學' then b.score else null end) [數學],        max(case c.Cname when N'英語' then b.score else null end) [英語],        cast(avg(b.score) as decimal(18,2)) 平均分 from Student a
left join SC b on a.S# = b.S# left join Course c on b.C# = c.C# group by a.S# , a.Sname order by 平均分 desc --17.2 SQL 2000 動態 declare @sql nvarchar(4000) set @sql = 'select a.S# ' + N'學生編號' + ' , a.Sname ' + N'學生姓名' select @sql = @sql + ',max(case c.Cname when N'''+Cname+''' then b.score else null end) ['+Cname+']' from (select distinct Cname from Course) as t set @sql = @sql + ' , cast(avg(b.score) as decimal(18,2)) ' + N'平均分' + ' from Student a left join SC b on a.S# = b.S# left join Course c on b.C# = c.C# group by a.S# , a.Sname order by ' + N'平均分' + ' desc' exec(@sql) --17.3 有關sql 2005的動靜態寫法參見個人文章《普通行列轉換(version 2.0)》或《普通行列轉換(version 3.0)》。

--1八、查詢各科成績最高分、最低分和平均分：以以下形式顯示：課程ID，課程name，最高分，最低分，平均分，及格率，中等率，優良率，優秀率 --及格爲>=60，中等爲：70-80，優良爲：80-90，優秀爲：>=90 --方法1 select m.C# [課程編號], m.Cname [課程名稱],   max(n.score) [最高分],   min(n.score) [最低分],   cast(avg(n.score) as decimal(18,2)) [平均分],   cast((select count(1) from SC where C# = m.C# and score >= 60)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [及格率(%)],   cast((select count(1) from SC where C# = m.C# and score >= 70 and score < 80 )*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [中等率(%)],   cast((select count(1) from SC where C# = m.C# and score >= 80 and score < 90 )*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [優良率(%)],   cast((select count(1) from SC where C# = m.C# and score >= 90)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [優秀率(%)] from Course m , SC n where m.C# = n.C# group by m.C# , m.Cname order by m.C# --方法2 select m.C# [課程編號], m.Cname [課程名稱],   (select max(score) from SC where C# = m.C#) [最高分],   (select min(score) from SC where C# = m.C#) [最低分],   (select cast(avg(score) as decimal(18,2)) from SC where C# = m.C#) [平均分],   cast((select count(1) from SC where C# = m.C# and score >= 60)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [及格率(%)],   cast((select count(1) from SC where C# = m.C# and score >= 70 and score < 80 )*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [中等率(%)],   cast((select count(1) from SC where C# = m.C# and score >= 80 and score < 90 )*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [優良率(%)],   cast((select count(1) from SC where C# = m.C# and score >= 90)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [優秀率(%)] from Course m order by m.C#

--1九、按各科成績進行排序，並顯示排名 --19.1 sql 2000用子查詢完成 --Score重複時保留名次空缺 select t.* , px = (select count(1) from SC where C# = t.C# and score > t.score) + 1 from sc t order by t.c# , px --Score重複時合併名次 select t.* , px = (select count(distinct score) from SC where C# = t.C# and score >= t.score) from sc t order by t.c# , px --19.2 sql 2005用rank,DENSE_RANK完成 --Score重複時保留名次空缺(rank完成) select t.* , px = rank() over(partition by c# order by score desc) from sc t order by t.C# , px
--Score重複時合併名次(DENSE_RANK完成) select t.* , px = DENSE_RANK() over(partition by c# order by score desc) from sc t order by t.C# , px

--20、查詢學生的總成績並進行排名 --20.1 查詢學生的總成績 select m.S# [學生編號] ,        m.Sname [學生姓名] ,        isnull(sum(score),0) [總成績] from Student m left join SC n on m.S# = n.S# group by m.S# , m.Sname order by [總成績] desc --20.2 查詢學生的總成績並進行排名，sql 2000用子查詢完成，分總分重複時保留名次空缺和不保留名次空缺兩種。 select t1.* , px = (select count(1) from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(sum(score),0) [總成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t2 where 總成績 > t1.總成績) + 1 from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(sum(score),0) [總成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t1 order by px

select t1.* , px = (select count(distinct 總成績) from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(sum(score),0) [總成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t2 where 總成績 >= t1.總成績) from (   select m.S# [學生編號] ,
         m.Sname [學生姓名] ,          isnull(sum(score),0) [總成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t1 order by px --20.3 查詢學生的總成績並進行排名，sql 2005用rank,DENSE_RANK完成，分總分重複時保留名次空缺和不保留名次空缺兩種。 select t.* , px = rank() over(order by [總成績] desc) from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(sum(score),0) [總成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t order by px

select t.* , px = DENSE_RANK() over(order by [總成績] desc) from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(sum(score),0) [總成績]   from Student m left join SC n on m.S# = n.S#
  group by m.S# , m.Sname ) t order by px

--2一、查詢不一樣老師所教不一樣課程平均分從高到低顯示 select m.T# , m.Tname , cast(avg(o.score) as decimal(18,2)) avg_score from Teacher m , Course n , SC o where m.T# = n.T# and n.C# = o.C# group by m.T# , m.Tname order by avg_score desc

--2二、查詢全部課程的成績第2名到第3名的學生信息及該課程成績 --22.1 sql 2000用子查詢完成 --Score重複時保留名次空缺 select * from (select t.* , px = (select count(1) from SC where C# = t.C# and score > t.score) + 1 from sc t) m where px between 2 and 3 order by m.c# , m.px --Score重複時合併名次 select * from (select t.* , px = (select count(distinct score) from SC where C# = t.C# and score >= t.score) from sc t) m where px between 2 and 3 order by m.c# , m.px
--22.2 sql 2005用rank,DENSE_RANK完成 --Score重複時保留名次空缺(rank完成) select * from (select t.* , px = rank() over(partition by c# order by score desc) from sc t) m where px between 2 and 3 order by m.C# , m.px
--Score重複時合併名次(DENSE_RANK完成) select * from (select t.* , px = DENSE_RANK() over(partition by c# order by score desc) from sc t) m where px between 2 and 3 order by m.C# , m.px

--2三、統計各科成績各分數段人數：課程編號,課程名稱,[100-85],[85-70],[70-60],[0-60]及所佔百分比 --23.1 統計各科成績各分數段人數：課程編號,課程名稱,[100-85],[85-70],[70-60],[0-60] --橫向顯示 select Course.C# [課程編號] , Cname as [課程名稱] ,   sum(case when score >= 85 then 1 else 0 end) [85-100],   sum(case when score >= 70 and score < 85 then 1 else 0 end) [70-85],   sum(case when score >= 60 and score < 70 then 1 else 0 end) [60-70],   sum(case when score < 60 then 1 else 0 end) [0-60] from sc , Course where SC.C# = Course.C# group by Course.C# , Course.Cname order by Course.C# --縱向顯示1(顯示存在的分數段) select m.C# [課程編號] , m.Cname [課程名稱] , 分數段 = (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) ,
  count(1) 數量 from Course m , sc n where m.C# = n.C# group by m.C# , m.Cname , (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) order by m.C# , m.Cname , 分數段 --縱向顯示2(顯示存在的分數段，不存在的分數段用0顯示) select m.C# [課程編號] , m.Cname [課程名稱] , 分數段 = (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) ,
  count(1) 數量 from Course m , sc n where m.C# = n.C# group by all m.C# , m.Cname , (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) order by m.C# , m.Cname , 分數段

--23.2 統計各科成績各分數段人數：課程編號,課程名稱,[100-85],[85-70],[70-60],[<60]及所佔百分比
--橫向顯示 select m.C# 課程編號, m.Cname 課程名稱,   (select count(1) from SC where C# = m.C# and score < 60) [0-60],   cast((select count(1) from SC where C# = m.C# and score < 60)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [百分比(%)],   (select count(1) from SC where C# = m.C# and score >= 60 and score < 70) [60-70],   cast((select count(1) from SC where C# = m.C# and score >= 60 and score < 70)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [百分比(%)],   (select count(1) from SC where C# = m.C# and score >= 70 and score < 85) [70-85],   cast((select count(1) from SC where C# = m.C# and score >= 70 and score < 85)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [百分比(%)],   (select count(1) from SC where C# = m.C# and score >= 85) [85-100],   cast((select count(1) from SC where C# = m.C# and score >= 85)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [百分比(%)] from Course m order by m.C# --縱向顯示1(顯示存在的分數段) select m.C# [課程編號] , m.Cname [課程名稱] , 分數段 = (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) ,   count(1) 數量 ,    cast(count(1) * 100.0 / (select count(1) from sc where C# = m.C#) as decimal(18,2)) [百分比(%)] from Course m , sc n where m.C# = n.C# group by m.C# , m.Cname , (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) order by m.C# , m.Cname , 分數段 --縱向顯示2(顯示存在的分數段，不存在的分數段用0顯示) select m.C# [課程編號] , m.Cname [課程名稱] , 分數段 = (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) ,   count(1) 數量 ,    cast(count(1) * 100.0 / (select count(1) from sc where C# = m.C#) as decimal(18,2)) [百分比(%)] from Course m , sc n where m.C# = n.C# group by all m.C# , m.Cname , (   case when n.score >= 85 then '85-100'        when n.score >= 70 and n.score < 85 then '70-85'        when n.score >= 60 and n.score < 70 then '60-70'        else '0-60'   end) order by m.C# , m.Cname , 分數段

        --2四、查詢學平生均成績及其名次 --24.1 查詢學生的平均成績並進行排名，sql 2000用子查詢完成，分平均成績重複時保留名次空缺和不保留名次空缺兩種。 select t1.* , px = (select count(1) from
(   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(cast(avg(score) as decimal(18,2)),0) [平均成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t2 where 平均成績 > t1.平均成績) + 1 from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(cast(avg(score) as decimal(18,2)),0) [平均成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t1 order by px

select t1.* , px = (select count(distinct 平均成績) from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(cast(avg(score) as decimal(18,2)),0) [平均成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t2 where 平均成績 >= t1.平均成績) from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(cast(avg(score) as decimal(18,2)),0) [平均成績]   from Student m left join SC n on m.S# = n.S#
  group by m.S# , m.Sname ) t1 order by px --24.2 查詢學生的平均成績並進行排名，sql 2005用rank,DENSE_RANK完成，分平均成績重複時保留名次空缺和不保留名次空缺兩種。 select t.* , px = rank() over(order by [平均成績] desc) from (   select m.S# [學生編號] ,
         m.Sname [學生姓名] ,          isnull(cast(avg(score) as decimal(18,2)),0) [平均成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t order by px

select t.* , px = DENSE_RANK() over(order by [平均成績] desc) from (   select m.S# [學生編號] ,          m.Sname [學生姓名] ,          isnull(cast(avg(score) as decimal(18,2)),0) [平均成績]   from Student m left join SC n on m.S# = n.S#   group by m.S# , m.Sname ) t order by px  
--2五、查詢各科成績前三名的記錄 --25.1 分數重複時保留名次空缺 select m.* , n.C# , n.score from Student m, SC n where m.S# = n.S# and n.score in (select top 3 score from sc where C# = n.C# order by score desc) order by n.C# , n.score desc --25.2 分數重複時不保留名次空缺，合併名次 --sql 2000用子查詢實現 select * from (select t.* , px = (select count(distinct score) from SC where C# = t.C# and score >= t.score) from sc t) m where px between 1 and 3 order by m.c# , m.px --sql 2005用DENSE_RANK實現 select * from (select t.* , px = DENSE_RANK() over(partition by c# order by score desc) from sc t) m where px between 1 and 3 order by m.C# , m.px

--2六、查詢每門課程被選修的學生數 select c# , count(S#)[學生數] from sc group by C#

--2七、查詢出只有兩門課程的所有學生的學號和姓名 select Student.S# , Student.Sname from Student , SC where Student.S# = SC.S# group by Student.S# , Student.Sname having count(SC.C#) = 2 order by Student.S#   --2八、查詢男生、女生人數 select count(Ssex) as 男生人數 from Student where Ssex = N'男' select count(Ssex) as 女生人數 from Student where Ssex = N'女' select sum(case when Ssex = N'男' then 1 else 0 end) [男生人數],sum(case when Ssex = N'女' then 1 else 0 end) [女生人數] from student select case when Ssex = N'男' then N'男生人數' else N'女生人數' end [男女狀況] , count(1) [人數] from student group by case when Ssex = N'男' then N'男生人數' else N'女生人數' end

--2九、查詢名字中含有"風"字的學生信息 select * from student where sname like N'%風%' select * from student where charindex(N'風' , sname) > 0

--30、查詢同名同性學生名單，並統計同名人數 select Sname [學生姓名], count(*) [人數] from Student group by Sname having count(*) > 1   --3一、查詢1990年出生的學生名單(注：Student表中Sage列的類型是datetime) select * from Student where year(sage) = 1990 select * from Student where datediff(yy,sage,'1990-01-01') = 0 select * from Student where datepart(yy,sage) = 1990 select * from Student where convert(varchar(4),sage,120) = '1990'

--3二、查詢每門課程的平均成績，結果按平均成績降序排列，平均成績相同時，按課程編號升序排列 select m.C# , m.Cname , cast(avg(n.score) as decimal(18,2)) avg_score from Course m, SC n where m.C# = n.C#    group by m.C# , m.Cname order by avg_score desc, m.C# asc

--3三、查詢平均成績大於等於85的全部學生的學號、姓名和平均成績 select a.S# , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.S# = b.S# group by a.S# , a.Sname having cast(avg(b.score) as decimal(18,2)) >= 85 order by a.S#

--3四、查詢課程名稱爲"數學"，且分數低於60的學生姓名和分數 select sname , score from Student , SC , Course where SC.S# = Student.S# and SC.C# = Course.C# and Course.Cname = N'數學' and score < 60

--3五、查詢全部學生的課程及分數狀況； select Student.* , Course.Cname , SC.C# , SC.score 
from Student, SC , Course where Student.S# = SC.S# and SC.C# = Course.C#
order by Student.S# , SC.C#

--3六、查詢任何一門課程成績在70分以上的姓名、課程名稱和分數； select Student.* , Course.Cname , SC.C# , SC.score  from Student, SC , Course where Student.S# = SC.S# and SC.C# = Course.C# and SC.score >= 70 order by Student.S# , SC.C#

--3七、查詢不及格的課程 select Student.* , Course.Cname , SC.C# , SC.score  from Student, SC , Course where Student.S# = SC.S# and SC.C# = Course.C# and SC.score < 60 order by Student.S# , SC.C#

--3八、查詢課程編號爲01且課程成績在80分以上的學生的學號和姓名； select Student.* , Course.Cname , SC.C# , SC.score  from Student, SC , Course where Student.S# = SC.S# and SC.C# = Course.C# and SC.C# = '01' and SC.score >= 80 order by Student.S# , SC.C#

--3九、求每門課程的學生人數 select Course.C# , Course.Cname , count(*) [學生人數] from Course , SC where Course.C# = SC.C# group by  Course.C# , Course.Cname order by Course.C# , Course.Cname

--40、查詢選修"張三"老師所授課程的學生中，成績最高的學生信息及其成績 --40.1 當最高分只有一個時 select top 1 Student.* , Course.Cname , SC.C# , SC.score  from Student, SC , Course , Teacher where Student.S# = SC.S# and SC.C# = Course.C# and Course.T# = Teacher.T# and Teacher.Tname = N'張三' order by SC.score desc --40.2 當最高分出現多個時 select Student.* , Course.Cname , SC.C# , SC.score  from Student, SC , Course , Teacher where Student.S# = SC.S# and SC.C# = Course.C# and Course.T# = Teacher.T# and Teacher.Tname = N'張三' and SC.score = (select max(SC.score) from SC , Course , Teacher where SC.C# = Course.C# and Course.T# = Teacher.T# and Teacher.Tname = N'張三')

--4一、查詢不一樣課程成績相同的學生的學生編號、課程編號、學生成績 --方法1 select m.* from SC m ,(select C# , score from SC group by C# , score having count(1) > 1) n where m.C#= n.C# and m.score = n.score order by m.C# , m.score , m.S# --方法2 select m.* from SC m where exists (select 1 from (select C# , score from SC group by C# , score having count(1) > 1) n where m.C#= n.C# and m.score = n.score) order by m.C# , m.score , m.S#

--4二、查詢每門功成績最好的前兩名 select t.* from sc t where score in (select top 2 score from sc where C# = T.C# order by score desc) order by t.C# , t.score desc

--4三、統計每門課程的學生選修人數（超過5人的課程才統計）。要求輸出課程號和選修人數，查詢結果按人數降序排列，若人數相同，按課程號升序排列 
select Course.C# , Course.Cname , count(*) [學生人數] from Course , SC
where Course.C# = SC.C# group by  Course.C# , Course.Cname having count(*) >= 5 order by [學生人數] desc , Course.C#

--4四、檢索至少選修兩門課程的學生學號 select student.S# , student.Sname from student , SC where student.S# = SC.S# group by student.S# , student.Sname
having count(1) >= 2 order by student.S#

--4五、查詢選修了所有課程的學生信息 --方法1 根據數量來完成 select student.* from student where S# in (select S# from sc group by S# having count(1) = (select count(1) from course)) --方法2 使用雙重否認來完成 select t.* from student t where t.S# not in
(   select distinct m.S# from   (     select S# , C# from student , course   ) m where not exists (select 1 from sc n where n.S# = m.S# and n.C# = m.C#) ) --方法3 使用雙重否認來完成 select t.* from student t where not exists(select 1 from (   select distinct m.S# from   (     select S# , C# from student , course   ) m where not exists (select 1 from sc n where n.S# = m.S# and n.C# = m.C#) ) k where k.S# = t.S# )

--4六、查詢各學生的年齡 --46.1 只按照年份來算 select * , datediff(yy , sage , getdate()) [年齡] from student --46.2 按照出生日期來算，當前月日 < 出生年月的月日則，年齡減一 select * , case when right(convert(varchar(10),getdate(),120),5) < right(convert(varchar(10),sage,120),5) then datediff(yy , sage , getdate()) - 1 else datediff(yy , sage , getdate()) end [年齡] from student

--4七、查詢本週過生日的學生 select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0

--4八、查詢下週過生日的學生 select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1

--4九、查詢本月過生日的學生 select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0

--50、查詢下月過生日的學生 select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1

drop table  Student,Course,Teacher,SC