[Java面试十一]数据库总结.

问题及描述： --1.学生表 Student(SID,Sname,Sage,Ssex) --SID 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别 --2.课程表 Course(CID,Cname,TID) --CID --课程编号,Cname 课程名称,TID 教师编号 --3.教师表 Teacher(TID,Tname) --TID 教师编号,Tname 教师姓名 --4.成绩表 SC(SID,CID,score) --SID 学生编号,CID 课程编号,score 分数 */ --创建测试数据 create table Student(SID varchar(10),Sname nvarchar(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(CID varchar(10),Cname nvarchar(10),TID 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(TID varchar(10),Tname nvarchar(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(SID varchar(10),CID 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);

--1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数 --1.1、查询同时存在"01"课程和"02"课程的情况 select a.* , b.score 课程01的分数,c.score 课程02的分数 from Student a , SC b , SC c where a.SID = b.SID and a.SID = c.SID and b.CID = '01' and c.CID = '02' and b.score > c.score --1.2、查询同时存在"01"课程和"02"课程的情况和存在"01"课程但可能不存在"02"课程的情况(不存在时显示为null)(以下存在相同内容时不再解释) select a.* , b.score 课程01的分数,c.score 课程02的分数 from Student a left join SC b on a.SID = b.SID and b.CID = '01' left join SC c on a.SID = c.SID and c.CID = '02' where b.score > isnull(c.score,0)

--2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数 --2.1、查询同时存在"01"课程和"02"课程的情况 select a.* , b.score  课程01的分数 ,c.score  课程02的分数  from Student a , SC b , SC c where a.SID = b.SID and a.SID = c.SID and b.CID = '01' and c.CID = '02' and b.score < c.score --2.2、查询同时存在"01"课程和"02"课程的情况和不存在"01"课程但存在"02"课程的情况 select a.* , b.score  课程01的分数 ,c.score  课程02的分数  from Student a left join SC b on a.SID = b.SID and b.CID = '01' left join SC c on a.SID = c.SID and c.CID = '02' where isnull(b.score,0) < c.score

--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.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.SID = b.SID group by a.SID , a.Sname having cast(avg(b.score) as decimal(18,2)) >= 60 order by a.SID

--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 --4.1、查询在sc表存在成绩的学生信息的SQL语句。 select a.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.SID = b.SID group by a.SID , a.Sname having cast(avg(b.score) as decimal(18,2)) < 60 order by a.SID --4.2、查询在sc表中不存在成绩的学生信息的SQL语句。 select a.SID , a.Sname , isnull(cast(avg(b.score) as decimal(18,2)),0) avg_score from Student a left join sc b on a.SID = b.SID group by a.SID , a.Sname having isnull(cast(avg(b.score) as decimal(18,2)),0) < 60 order by a.SID

--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 --5.1、查询所有有成绩的SQL。 select a.SID  学生编号 , a.Sname  学生姓名 , count(b.CID) 选课总数, sum(score)  所有课程的总成绩 from Student a , SC b where a.SID = b.SID group by a.SID,a.Sname order by a.SID --5.2、查询所有(包括有成绩和无成绩)的SQL。 select a.SID  学生编号 , a.Sname  学生姓名 , count(b.CID) 选课总数, sum(score)  所有课程的总成绩 from Student a left join SC b on a.SID = b.SID group by a.SID,a.Sname order by a.SID

--6、查询"李"姓老师的数量 --方法1 select count(Tname)  李姓老师的数量  from Teacher where Tname like '李%' --方法2 select count(Tname)  李姓老师的数量  from Teacher where left(Tname,1) = '李'

--7、查询学过"张三"老师授课的同学的信息 select distinct Student.* from Student , SC , Course , Teacher where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = '张三' order by Student.SID

--8、查询没学过"张三"老师授课的同学的信息 select m.* from Student m where SID not in (select distinct SC.SID from SC , Course , Teacher where SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = '张三') order by m.SID

--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 --方法1 select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID --方法2 select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '02' and exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '01') order by Student.SID --方法3 select m.* from Student m where SID in (   select SID from   (     select distinct SID from SC where CID = '01'     union all     select distinct SID from SC where CID = '02'   ) t group by SID having count(1) = 2 ) order by m.SID

--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 --方法1 select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and not exists (Select 1 from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID --方法2 select Student.* from Student , SC where Student.SID = SC.SID and SC.CID = '01' and Student.SID not in (Select SC_2.SID from SC SC_2 where SC_2.SID = SC.SID and SC_2.CID = '02') order by Student.SID

--11、查询没有学全所有课程的同学的信息 --11.1、 select Student.* from Student , SC where Student.SID = SC.SID group by Student.SID , Student.Sname , Student.Sage , Student.Ssex having count(CID) < (select count(CID) from Course) --11.2 select Student.* from Student left join SC on Student.SID = SC.SID group by Student.SID , Student.Sname , Student.Sage , Student.Ssex having count(CID) < (select count(CID) from Course)

--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 distinct Student.* from Student , SC where Student.SID = SC.SID and SC.CID in (select CID from SC where SID = '01') and Student.SID <> '01'

--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 Student.* from Student where SID in (select distinct SC.SID from SC where SID <> '01' and SC.CID in (select distinct CID from SC where SID = '01') group by SC.SID having count(1) = (select count(1) from SC where SID='01'))

--14、查询没学过"张三"老师讲授的任一门课程的学生姓名 select student.* from student where student.SID not in (select distinct sc.SID from sc , course , teacher where sc.CID = course.CID and course.TID = teacher.TID and teacher.tname = '张三') order by student.SID

--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 student.SID , student.sname , cast(avg(score) as decimal(18,2)) avg_score from student , sc where student.SID = SC.SID and student.SID in (select SID from SC where score < 60 group by SID having count(1) >= 2) group by student.SID , student.sname

--16、检索"01"课程分数小于60，按分数降序排列的学生信息 select student.* , sc.CID , sc.score from student , sc where student.SID = SC.SID and sc.score < 60 and sc.CID = '01' order by sc.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 --17.1 SQL 2000 静态 select a.SID 学生编号 , a.Sname 学生姓名 ,        max(case c.Cname when '语文' then b.score else null end)  语文 ,        max(case c.Cname when '数学' then b.score else null end)  数学 ,        max(case c.Cname when '英语' then b.score else null end)  英语 ,        cast(avg(b.score) as decimal(18,2)) 平均分 from Student a left join SC b on a.SID = b.SID left join Course c on b.CID = c.CID group by a.SID , a.Sname order by 平均分 desc --17.2 SQL 2000 动态 declare @sql nvarchar(4000) set @sql = 'select a.SID ' + '学生编号' + ' , a.Sname ' + '学生姓名' select @sql = @sql + ',max(case c.Cname when '''+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)) ' + '平均分' + ' from Student a left join SC b on a.SID = b.SID left join Course c on b.CID = c.CID group by a.SID , a.Sname order by ' + '平均分' + ' desc' exec(@sql)

--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：>=90 --方法1 select m.CID 课程编号 , m.Cname 课程名称 , 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 CID = m.CID and score >= 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 及格率 , cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 80 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 中等率 , cast((select count(1) from SC where CID = m.CID and score >= 80 and score < 90 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优良率 , cast((select count(1) from SC where CID = m.CID and score >= 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优秀率 from Course m , SC n where m.CID = n.CID group by m.CID , m.Cname order by m.CID --方法2 select m.CID 课程编号 , m.Cname 课程名称 ,   (select max(score) from SC where CID = m.CID) 最高分 ,   (select min(score) from SC where CID = m.CID) 最低分 ,   (select cast(avg(score) as decimal(18,2)) from SC where CID = m.CID) 平均分 , cast((select count(1) from SC where CID = m.CID and score >= 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 及格率, cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 80 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 中等率 , cast((select count(1) from SC where CID = m.CID and score >= 80 and score < 90 )*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优良率 , cast((select count(1) from SC where CID = m.CID and score >= 90)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 优秀率 from Course m order by m.CID --19、按各科成绩进行排序，并显示排名 --19.1 sql 2000用子查询完成 --Score重复时保留名次空缺 select t.* , px = (select count(1) from SC where CID = t.CID and score > t.score) + 1 from sc t order by t.cid , px --Score重复时合并名次 select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t order by t.cid , px --19.2 sql 2005用rank,DENSE_RANK完成 --Score重复时保留名次空缺(rank完成) select t.* , px = rank() over(partition by cid order by score desc) from sc t order by t.CID , px --Score重复时合并名次(DENSE_RANK完成) select t.* , px = DENSE_RANK() over(partition by cid order by score desc) from sc t order by t.CID , px --20、查询学生的总成绩并进行排名 --20.1 查询学生的总成绩 select m.SID 学生编号 ,        m.Sname 学生姓名 , isnull(sum(score),0) 总成绩 from Student m left join SC n on m.SID = n.SID group by m.SID , m.Sname order by 总成绩 desc --20.2 查询学生的总成绩并进行排名，sql 2000用子查询完成，分总分重复时保留名次空缺和不保留名次空缺两种。 select t1.* , px = (select count(1) from ( select m.SID 学生编号 ,          m.Sname 学生姓名 , isnull(sum(score),0) 总成绩 from Student m left join SC n on m.SID = n.SID group by m.SID , m.Sname ) t2 where 总成绩 > t1.总成绩) + 1 from ( select m.SID 学生编号 ,          m.Sname 学生姓名 , isnull(sum(score),0) 总成绩 from Student m left join SC n on m.SID = n.SID group by m.SID , m.Sname ) t1 order by px select t1.* , px = (select count(distinct 总成绩) from ( select m.SID 学生编号 ,          m.Sname 学生姓名 , isnull(sum(score),0) 总成绩 from Student m left join SC n on m.SID = n.SID group by m.SID , m.Sname ) t2 where 总成绩 >= t1.总成绩) from ( select m.SID 学生编号 ,          m.Sname 学生姓名 , isnull(sum(score),0) 总成绩 from Student m left join SC n on m.SID = n.SID group by m.SID , m.Sname ) t1 order by px --20.3 查询学生的总成绩并进行排名，sql 2005用rank,DENSE_RANK完成，分总分重复时保留名次空缺和不保留名次空缺两种。 select t.* , px = rank() over(order by 总成绩 desc) from ( select m.SID 学生编号 ,          m.Sname 学生姓名 , isnull(sum(score),0) 总成绩 from Student m left join SC n on m.SID = n.SID group by m.SID , m.Sname ) t order by px select t.* , px = DENSE_RANK() over(order by 总成绩 desc) from ( select m.SID 学生编号 ,          m.Sname 学生姓名 , isnull(sum(score),0) 总成绩 from Student m left join SC n on m.SID = n.SID group by m.SID , m.Sname ) t order by px --21、查询不同老师所教不同课程平均分从高到低显示 select m.TID , m.Tname , cast(avg(o.score) as decimal(18,2)) avg_score from Teacher m , Course n , SC o where m.TID = n.TID and n.CID = o.CID group by m.TID , m.Tname order by avg_score desc --22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩 --22.1 sql 2000用子查询完成 --Score重复时保留名次空缺 select * from (select t.* , px = (select count(1) from SC where CID = t.CID and score > t.score) + 1 from sc t) m where px between 2 and 3 order by m.cid , m.px --Score重复时合并名次 select * from (select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t) m where px between 2 and 3 order by m.cid , m.px --22.2 sql 2005用rank,DENSE_RANK完成 --Score重复时保留名次空缺(rank完成) select * from (select t.* , px = rank() over(partition by cid order by score desc) from sc t) m where px between 2 and 3 order by m.CID , m.px --Score重复时合并名次(DENSE_RANK完成) select * from (select t.* , px = DENSE_RANK() over(partition by cid order by score desc) from sc t) m where px between 2 and 3 order by m.CID , m.px --23、统计各科成绩各分数段人数：课程编号,课程名称, 100-85 , 85-70 , 70-60 , 0-60 及所占百分比 --23.1 统计各科成绩各分数段人数：课程编号,课程名称, 100-85 , 85-70 , 70-60 , 0-60 --横向显示 select Course.CID 课程编号 , Cname as 课程名称 , 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.CID = Course.CID group by Course.CID , Course.Cname order by Course.CID --纵向显示1(显示存在的分数段) select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = ( 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) 数量 from Course m , sc n where m.CID = n.CID group by m.CID , 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.CID , m.Cname , 分数段 --纵向显示2(显示存在的分数段，不存在的分数段用0显示) select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = ( 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) 数量 from Course m , sc n where m.CID = n.CID group by all m.CID , 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.CID , m.Cname , 分数段 --23.2 统计各科成绩各分数段人数：课程编号,课程名称, 100-85 , 85-70 , 70-60 , <60 及所占百分比 --横向显示 select m.CID 课程编号, m.Cname 课程名称,   (select count(1) from SC where CID = m.CID and score < 60) 0-60 , cast((select count(1) from SC where CID = m.CID and score < 60)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,   (select count(1) from SC where CID = m.CID and score >= 60 and score < 70) 60-70 , cast((select count(1) from SC where CID = m.CID and score >= 60 and score < 70)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,   (select count(1) from SC where CID = m.CID and score >= 70 and score < 85) 70-85 , cast((select count(1) from SC where CID = m.CID and score >= 70 and score < 85)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 ,   (select count(1) from SC where CID = m.CID and score >= 85) 85-100 , cast((select count(1) from SC where CID = m.CID and score >= 85)*100.0 / (select count(1) from SC where CID = m.CID) as decimal(18,2)) 百分比 from Course m order by m.CID --纵向显示1(显示存在的分数段) select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = ( 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) 数量 ,  cast(count(1) * 100.0 / (select count(1) from sc where CID = m.CID) as decimal(18,2)) 百分比 from Course m , sc n where m.CID = n.CID group by m.CID , 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.CID , m.Cname , 分数段 --纵向显示2(显示存在的分数段，不存在的分数段用0显示) select m.CID 课程编号 , m.Cname 课程名称 , 分数段 = ( 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) 数量 ,  cast(count(1) * 100.0 / (select count(1) from sc where CID = m.CID) as decimal(18,2)) 百分比 from Course m , sc n where m.CID = n.CID group by all m.CID , 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.CID , m.Cname , 分数段

--24、查询学生平均成绩及其名次 --24.1 查询学生的平均成绩并进行排名，sql 2000用子查询完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。 select t1.* , px = (select count(1) from (   select m.SID  学生编号  ,          m.Sname  学生姓名  ,          isnull(cast(avg(score) as decimal(18,2)),0)  平均成绩   from Student m left join SC n on m.SID = n.SID   group by m.SID , m.Sname ) t2 where 平均成绩 > t1.平均成绩) + 1 from (   select m.SID  学生编号  ,          m.Sname  学生姓名  ,          isnull(cast(avg(score) as decimal(18,2)),0)  平均成绩   from Student m left join SC n on m.SID = n.SID   group by m.SID , m.Sname ) t1 order by px

select t1.* , px = (select count(distinct 平均成绩) from (   select m.SID  学生编号  ,          m.Sname  学生姓名  ,          isnull(cast(avg(score) as decimal(18,2)),0)  平均成绩   from Student m left join SC n on m.SID = n.SID   group by m.SID , m.Sname ) t2 where 平均成绩 >= t1.平均成绩) from (   select m.SID  学生编号  ,          m.Sname  学生姓名  ,          isnull(cast(avg(score) as decimal(18,2)),0)  平均成绩   from Student m left join SC n on m.SID = n.SID   group by m.SID , m.Sname ) t1 order by px --24.2 查询学生的平均成绩并进行排名，sql 2005用rank,DENSE_RANK完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。 select t.* , px = rank() over(order by  平均成绩  desc) from (   select m.SID  学生编号  ,          m.Sname  学生姓名  ,          isnull(cast(avg(score) as decimal(18,2)),0)  平均成绩   from Student m left join SC n on m.SID = n.SID   group by m.SID , m.Sname ) t order by px

select t.* , px = DENSE_RANK() over(order by  平均成绩  desc) from (   select m.SID  学生编号  ,          m.Sname  学生姓名  ,          isnull(cast(avg(score) as decimal(18,2)),0)  平均成绩   from Student m left join SC n on m.SID = n.SID   group by m.SID , m.Sname ) t order by px --25、查询各科成绩前三名的记录 --25.1 分数重复时保留名次空缺 select m.* , n.CID , n.score from Student m, SC n where m.SID = n.SID and n.score in (select top 3 score from sc where CID = n.CID order by score desc) order by n.CID , n.score desc --25.2 分数重复时不保留名次空缺，合并名次 --sql 2000用子查询实现 select * from (select t.* , px = (select count(distinct score) from SC where CID = t.CID and score >= t.score) from sc t) m where px between 1 and 3 order by m.Cid , m.px --sql 2005用DENSE_RANK实现 select * from (select t.* , px = DENSE_RANK() over(partition by Cid order by score desc) from sc t) m where px between 1 and 3 order by m.CID , m.px

--26、查询每门课程被选修的学生数 select Cid , count(SID) 学生数  from sc group by CID

--27、查询出只有两门课程的全部学生的学号和姓名 select Student.SID , Student.Sname from Student , SC where Student.SID = SC.SID group by Student.SID , Student.Sname having count(SC.CID) = 2 order by Student.SID

--28、查询男生、女生人数 select count(Ssex) as 男生人数 from Student where Ssex = N'男' select count(Ssex) as 女生人数 from Student where Ssex = N'女' select sum(case when Ssex = N'男' then 1 else 0 end)  男生人数 ,sum(case when Ssex = N'女' then 1 else 0 end)  女生人数  from student select case when Ssex = N'男' then N'男生人数' else N'女生人数' end  男女情况  , count(1)  人数  from student group by case when Ssex = N'男' then N'男生人数' else N'女生人数' end

--29、查询名字中含有"风"字的学生信息 select * from student where sname like N'%风%' select * from student where charindex(N'风' , sname) > 0

--30、查询同名同性学生名单，并统计同名人数 select Sname  学生姓名 , count(*)  人数  from Student group by Sname having count(*) > 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 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'

--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，按课程编号升序排列 select m.CID , m.Cname , cast(avg(n.score) as decimal(18,2)) avg_score from Course m, SC n where m.CID = n.CID   group by m.CID , m.Cname order by avg_score desc, m.CID asc

--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.SID , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.SID = b.SID group by a.SID , a.Sname having cast(avg(b.score) as decimal(18,2)) >= 85 order by a.SID

--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 sname , score from Student , SC , Course where SC.SID = Student.SID and SC.CID = Course.CID and Course.Cname = N'数学' and score < 60

--35、查询所有学生的课程及分数情况； select Student.* , Course.Cname , SC.CID , SC.score from Student, SC , Course where Student.SID = SC.SID and SC.CID = Course.CID order by Student.SID , SC.CID

--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 Student.* , Course.Cname , SC.CID , SC.score from Student, SC , Course where Student.SID = SC.SID and SC.CID = Course.CID and SC.score >= 70 order by Student.SID , SC.CID

--37、查询不及格的课程 select Student.* , Course.Cname , SC.CID , SC.score from Student, SC , Course where Student.SID = SC.SID and SC.CID = Course.CID and SC.score < 60 order by Student.SID , SC.CID

--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 Student.* , Course.Cname , SC.CID , SC.score from Student, SC , Course where Student.SID = SC.SID and SC.CID = Course.CID and SC.CID = '01' and SC.score >= 80 order by Student.SID , SC.CID

--39、求每门课程的学生人数 select Course.CID , Course.Cname , count(*)  学生人数 from Course , SC where Course.CID = SC.CID group by  Course.CID , Course.Cname order by Course.CID , Course.Cname

--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 --40.1 当最高分只有一个时 select top 1 Student.* , Course.Cname , SC.CID , SC.score from Student, SC , Course , Teacher where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'张三' order by SC.score desc --40.2 当最高分出现多个时 select Student.* , Course.Cname , SC.CID , SC.score from Student, SC , Course , Teacher where Student.SID = SC.SID and SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'张三' and SC.score = (select max(SC.score) from SC , Course , Teacher where SC.CID = Course.CID and Course.TID = Teacher.TID and Teacher.Tname = N'张三')

--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 --方法1 select m.* from SC m ,(select CID , score from SC group by CID , score having count(1) > 1) n where m.CID= n.CID and m.score = n.score order by m.CID , m.score , m.SID --方法2 select m.* from SC m where exists (select 1 from (select CID , score from SC group by CID , score having count(1) > 1) n where m.CID= n.CID and m.score = n.score) order by m.CID , m.score , m.SID

--42、查询每门功成绩最好的前两名 select t.* from sc t where score in (select top 2 score from sc where CID = T.CID order by score desc) order by t.CID , t.score desc

--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 Course.CID , Course.Cname , count(*)  学生人数 from Course , SC where Course.CID = SC.CID group by  Course.CID , Course.Cname having count(*) >= 5 order by  学生人数  desc , Course.CID

--44、检索至少选修两门课程的学生学号 select student.SID , student.Sname from student , SC where student.SID = SC.SID group by student.SID , student.Sname having count(1) >= 2 order by student.SID

--45、查询选修了全部课程的学生信息 --方法1 根据数量来完成 select student.* from student where SID in (select SID from sc group by SID having count(1) = (select count(1) from course)) --方法2 使用双重否定来完成 select t.* from student t where t.SID not in (   select distinct m.SID from   (     select SID , CID from student , course   ) m where not exists (select 1 from sc n where n.SID = m.SID and n.CID = m.CID) ) --方法3 使用双重否定来完成 select t.* from student t where not exists(select 1 from (   select distinct m.SID from   (     select SID , CID from student , course   ) m where not exists (select 1 from sc n where n.SID = m.SID and n.CID = m.CID) ) k where k.SID = t.SID )

--46、查询各学生的年龄 --46.1 只按照年份来算 select * , datediff(yy , sage , getdate())  年龄  from student --46.2 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一 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  年龄  from student

--47、查询本周过生日的学生 select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0

--48、查询下周过生日的学生 select * from student where datediff(week,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1

--49、查询本月过生日的学生 select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = 0

--50、查询下月过生日的学生 select * from student where datediff(mm,datename(yy,getdate()) + right(convert(varchar(10),sage,120),6),getdate()) = -1

drop table  Student,Course,Teacher,SC