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);
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;
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);
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;
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) < c.score;
如要显示没选课的学生(显示为NULL),需要使用join:
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;
CAST函数用于将某种数据类型的表达式显式转换为另一种数据类型。CAST()函数的参数是一个表达式,它包括用AS关键字分隔的源值和目标数据类型。
CAST (expressionASdata_type);
decimal(a,b)
a指定指定小数点左边和右边可以存储的十进制数字的最大个数,最大精度38。
b指定小数点右边可以存储的十进制数字的最大个数。小数位数必须是从 0 到 a之间的值。默认小数位数是 0。
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
selecta.SID, a.Sname,cast(avg(b.score)as decimal(18,2)) avg_score
fromStudent aleft joinsc b
ona.SID= b.SID**
group bya.SID, a.Sname
**havingcast(avg(b.score)as decimal(18,2)) < 60
order bya.SID;
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
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
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’
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
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
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
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
11.1、
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)
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’
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’))
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
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
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
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
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)
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 >=70and 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 >=80and 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 >=70and 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 >=80and 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
Score重复时保留名次空缺
select t.* , (select count(1) from SC where CID = t.CID and score > t.score) + 1 px from sc t order by t.cid , px;
方法二(推荐):
selectt.*** , (selectcount(score)fromSCwhereCID= t.CIDandscore> t.score) +1 pxfromsc torder byt.cid, px;
Score重复时合并名次
select t.* , (select count(distinct score) from SC where CID = t.CID and score >= t.score) px from sc t order by t.cid , px;
方法二(推荐):
selectt.*** , (selectcount(distinctscore)fromSCwhereCID= t.CIDandscore> t.score) +1 pxfromsc torder byt.cid, px;
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
select m.SID 学生编号 ,
m.Sname 学生姓名 ,
sum(score) 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;
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) +1from
(
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
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
selectm.TID,n.Cname, m.Tname,cast(avg(o.score)as decimal(18,2)) avg_score
fromTeacher m , Course n , SC o
wherem.TID= n.TIDandn.CID= o.CID**
group bym.TID, n.Cname, m.Tname
**order byavg_scoredesc;
Score重复时保留名次空缺
方法一:selectfrom(selectt. , (selectcount(1)fromSCwhereCID= t.CIDandscore> t.score) + 1 pxfromsc t) mwherepxbetween2and3order bym.cid;
方法二(推荐):selectt.,(selectcount(score)fromscwherecid=t.cidandscore>t.score) +1 pxfromsc thavingpx>=2andpx<=3order byt.cid,px;
Score重复时合并名次
方法一:selectfrom(selectt. , (selectcount(distinctscore)fromSCwhereCID= t.CIDandscore>= t.score) pxfromsc t) mwherepxbetween2and3order bym.cid;
方法二(推荐):selectt. , (selectcount(distinctscore)fromSCwhereCID= t.CIDandscore> t.score) + 1 pxfromsc thavingpx>=2andpx<=3order byt.cid, px;
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 between2and3order 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 between2and3order by m.CID , m.px
横向显示
selectCourse.CID课程编号 ,Cnameas课程名称 ,
sum(case whenscore>= 85then1else0end)‘85-100’,
sum(case whenscore>= 70andscore< 85then1else0end)‘70-85’,
sum(case whenscore>= 60andscore< 70then1else0end)‘60-70’,
sum(case whenscore< 60then1else0end)‘0-60’**
fromsc , Course
whereSC.CID= Course.CID**
group byCourse.CID, Course.Cname
order byCourse.CID;
纵向显示1(显示存在的分数段)
selectm.CID课程编号 , m.Cname课程名称 , (
case whenn.score>= 85then‘85-100’**
whenn.score>= 70andn.score< 85then‘70-85’**
whenn.score>= 60andn.score< 70then‘60-70’**
else‘0-60’**
end) 分数段 ,
count(1) 数量
fromCourse m , sc n
wherem.CID= n.CID**
group bym.CID, m.Cname, (
case whenn.score>= 85then'85-100’
whenn.score>= 70andn.score< 85then‘70-85’**
whenn.score>= 60andn.score< 70then‘60-70’**
else‘0-60’**
end)
order bym.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)
selectm.CID课程编号 , m.Cname课程名称 , (
case whenn.score>= 85then‘85-100’**
whenn.score>= 70andn.score< 85then‘70-85’**
whenn.score>= 60andn.score< 70then‘60-70’**
else‘0-60’**
end) 分数段,
count(1) 数量
fromCourse m , sc n
wherem.CID= n.CID**
group bym.CID, m.Cname, (
case whenn.score>= 85then'85-100’
whenn.score>= 70andn.score< 85then‘70-85’**
whenn.score>= 60andn.score< 70then‘60-70’**
else‘0-60’**
end)
order bym.CID, m.Cname, 分数段;
横向显示
selectm.CID课程编号, m.Cname课程名称,
(selectcount(1)fromSCwhereCID= m.CIDandscore< 60)‘0-60’,
cast((selectcount(1)fromSCwhereCID= m.CIDandscore< 60)*100.0 / (selectcount(1)fromSCwhereCID= m.CID)as decimal(18,2)) 百分比 ,
(selectcount(1)fromSCwhereCID= m.CIDandscore>= 60andscore< 70)‘60-70’,
cast((selectcount(1)fromSCwhereCID= m.CIDandscore>= 60andscore< 70)*100.0 / (selectcount(1)fromSCwhereCID= m.CID)as decimal(18,2)) 百分比 ,
(selectcount(1)fromSCwhereCID= m.CIDandscore>= 70andscore< 85)‘70-85’,
cast((selectcount(1)fromSCwhereCID= m.CIDandscore>= 70andscore< 85)*100.0 / (selectcount(1)fromSCwhereCID= m.CID)as decimal(18,2)) 百分比 ,
(selectcount(1)fromSCwhereCID= m.CIDandscore>= 85)‘85-100’,
cast((selectcount(1)fromSCwhereCID= m.CIDandscore>= 85)*100.0 / (selectcount(1)fromSCwhereCID= m.CID)as decimal(18,2)) 百分比
fromCourse m
order bym.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 , (
case when n.score >=85then ‘85-100’
when n.score >=70and n.score <85then ‘70-85’
when n.score >=60and n.score <70then ‘60-70’
else ‘0-60’
end) 分数段,
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 >=85then ‘85-100’
when n.score >=70and n.score <85then ‘70-85’
when n.score >=60and n.score <70then ‘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)
selectm.CID课程编号 , m.Cname课程名称 ,(
case whenn.score>= 85then‘85-100’**
**whenn.score>= 70andn.score< 85then‘70-85’**
**whenn.score>= 60andn.score< 70then‘60-70’**
**else‘0-60’**
**end) 分数段,
count(1) 数量 ,
cast(count(1) * 100.0 / (selectcount(1)fromscwhereCID= m.CID)as decimal(18,2)) 百分比
fromCourse m , sc n
wherem.CID= n.CID**
group bym.CID, m.Cname, (
case whenn.score>= 85then'85-100’
**whenn.score>= 70andn.score< 85then‘70-85’**
**whenn.score>= 60andn.score< 70then‘60-70’**
**else‘0-60’**
**end)
order bym.CID, m.Cname, 分数段;
方法一(推荐):
selecta.sid学生编号,a.sname学生姓名,cast(avg(b.score)as decimal(18,2)) 平均成绩,
(selectcount(***)fromscwheresc.cid=b.cidandsc.score>=b.score)+1 px
fromstudent aleft joinsc bona.sid=b.sidgroup bya.sid,a.snameorder bypx;
selectt1.*** , (selectcount(1)from**
** (
selectm.SID学生编号 ,
m.Sname学生姓名 ,
cast(avg(score)as decimal(18,2)) 平均成绩
fromStudent mleft joinSC nonm.SID= n.SID**
**group bym.SID, m.Sname**
** ) t2where平均成绩 > t1.平均成绩) + 1 pxfrom**
** (
selectm.SID学生编号 ,
m.Sname学生姓名 ,
cast(avg(score)as decimal(18,2)) 平均成绩
fromStudent mleft joinSC nonm.SID= n.SID**
**group bym.SID, m.Sname**
** ) t1
order bypx;
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
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
SELECTa.*,COUNT(B.score) +1asranking
FROMSC aLEFT JOINSC b
ONa.CId= b.CIdANDa.score<b.score
GROUP BYa.CId,a.SId,a.score
**HAVINGranking <= 3
ORDER BYa.CId,ranking;
sql 2000用子查询实现
select***from(selectt.*** , (selectcount(distinctscore)fromSCwhereCID= t.CIDandscore>= t.score) pxfromsc t) mwherepxbetween1and3order bym.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
selectsc.Cid,course.Cname,count(SID) 学生数fromcourse,scwherecourse.cid=sc.cidgroup byCID;
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;
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;
select * from student where sname like N’%风%’;
select Sname 学生姓名 , count() 人数 from Student group by Sname having count() > 1;
select***fromstudentwhereSagelike‘1990%’;
select * from Student where year(sage) = 1990;
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;
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;
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;
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
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
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
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;
selectCourse.CID, Course.Cname,count(1) 学生人数
fromcourse,sc
wherecourse.cid=sc.CID**
group byCourse.CID, Course.Cname
**order byCourse.CID, Course.Cname;
select CId,count(SId)
from sc group by sc.CId
SELECTStudent.,SC.CId,score
FROMStudentJOINSCONStudent.SId= SC.SId
**JOINCourseONSC.CId= Course.CId*
**JOINTeacherONCourse.TId= Teacher.TId**
WHERETname='张三’
**ORDER BYscoreDESC LIMIT1;
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’);
SELECTStudent.,SC.CId,score
FROMStudentJOINSCONStudent.SId= SC.SId
**JOINCourseONSC.CId= Course.CId*
**JOINTeacherONCourse.TId= Teacher.TId**
WHERETname=‘张三’ANDscoreIN
** (SELECTMAX(score)FROM**
** SCJOINCourseONSC.CId= Course.CId**
**JOINTeacherONCourse.TId= Teacher.TId**
**WHERETname=‘张三’);
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
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;
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
select * , datediff(yy , sage , getdate()) 年龄 from student
selectSname,Sage,
year(now())-year(Sage)as年龄
fromstudent;
SELECTSId,Sname,TIMESTAMPDIFF(YEAR,Sage,NOW())AS年龄
FROMStudent;
SELECT***FROMstudentwhere**
**week(Sage)=week(now());
48、查询下周过生日的学生
SELECT***FROMstudentwhere**
**week(Sage)=week(now())+1;
SELECT***FROMstudent
wheremonth(Sage)=month(now());
SELECT***FROMstudent
wheremonth(Sage)=month(now())+1;