比较经典的sql

学生成绩表(stuscore)：
姓名：name
课程：subject
分数：score
学号：stuid
张三
数学
89
1
张三
语文
80
1
张三
英语
70
1
李四
数学
90
2
李四
语文
70
2
李四
英语
80
2




创建表
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for t_stusore
-- ----------------------------
DROP TABLE IF EXISTS `t_stuscore`;
CREATE TABLE `t_stuscore` (
  `name` varchar(32) default NULL,
  `subject` varchar(32) default NULL,
  `score` varchar(32) default NULL,
  `stuid` varchar(32) default NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;



插入数据 sql


INSERT INTO t_stuscore (`name`, `subject`, `score`, `stuid`) VALUES
   ('张三', '语文', '88', '1'),('张三', '数学', '77', '1'),('张三', '英语', '99', '1');

INSERT INTO t_stuscore (`name`, `subject`, `score`, `stuid`) VALUES
   ('李四', '语文', '98', '2'),('李四', '数学', '88', '2'),('李四', '英语', '98', '2');



问题：
1.计算每个人的总成绩并排名(要求显示字段：姓名，总成绩)

select  name as 姓名,
sum(score) as 总成绩
from t_stuscore T  group by T.name order by 总成绩;


2.计算每个人的总成绩并排名(要求显示字段: 学号，姓名，总成绩)

select T.STUID as 学号,name as 姓名,
sum(score) as 总成绩
from t_stuscore T  group by T.name order by 总成绩 desc;


 <  多表关联中使用  >
select distinct  t1.name, t1.stuid, t2.allscore
from  t_stuscore t1,(    select stuid,sum(score) as allscore from t_stuscore group by stuid)  t2
where t1.stuid=t2.stuid order by t2.allscore desc



3.计算每个人单科的最高成绩(要求显示字段: 学号，姓名，课程，最高成绩)

select t1.stuid,t1.name,t1.subject,t1.score
from t_stuscore t1,(select stuid,max(score) as maxscore from t_stuscore group by stuid) t2
where t1.stuid=t2.stuid and t1.score=t2.maxscore

*100的成绩统计不出来  int类型没有问题

4.计算每个人的平均成绩（要求显示字段: 学号，姓名，平均成绩）

select stuid, name, avg(score) as avgscore from t_stuscore group by stuid

或

select distinct t1.stuid,t1.name,t2.avgscore
from t_stuscore t1,(select stuid,avg(score) as avgscore from t_stuscore group by stuid) t2
where t1.stuid=t2.stuid


5.列出各门课程成绩最好的学生(要求显示字段: 学号，姓名,科目，成绩)


select  t1.stuid,t1.name,t1.subject, t2.maxscore
from t_stuscore t1,(select subject,max(score) as maxscore from t_stuscore group by subject ) t2
where t1.subject=t2.subject and t1.score = t2.maxscore;

6.列出各门课程成绩最好的两位学生(要求显示字段: 学号，姓名,科目，成绩)   

？？？

select distinct t1.* from t_stuscore t1 where t1.id in (
select top 2 t2.id from t_stuscore t2 where t2.subject = t1.subject order by t2.score desc
) order by t1.subject



7.统计如下：
学号
姓名
语文
数学
英语
总分
平均分









select T.STUID as 学号,name as 姓名,
sum(case when T.SUBJECT='语文' then T.SCORE else 0 end) as 语文,
sum(case when T.SUBJECT='数学' then T.SCORE else 0 end) as 数学,
sum(case when T.SUBJECT='英语' then T.SCORE else 0 end) as 英语
from t_stuscore T  group by T.STUID


select stuid as 学号,name as 姓名,
sum(case when subject='语文' then score else 0 end) as 语文,
sum(case when subject='数学' then score else 0 end) as 数学,
sum(case when subject='英语' then score else 0 end) as 英语,
sum(score) as 总分,
(sum(score)/count(*)) as 平均分
from t_stuscore group by stuid,name order by 总分 desc


8．列出各门课程的平均成绩（要求显示字段：课程，平均成绩）

select subject,avg(score) as avgscore from t_stuscore group by subject order by avgscore desc 


9．列出数学成绩的排名（要求显示字段：学号，姓名，成绩，排名）


？？？

declare @tmp table(pm int,name varchar(50),score int,stuid int) insert into @tmp
select null,name,score,stuid from t_stuscore where subject='数学'
order by score descdeclare @id intset @id=0;
update @tmp set @id=@id+1,pm=@idselect * from @tmp


select  DENSE_RANK () OVER( order by score desc ) as row,name,subject,score,stuid
from t_stuscore where subject='数学' order by score desc


10．列出数学成绩在2-3名的学生（要求显示字段：学号，姓名,科目，成绩）


？？？

select t3.*  from(
    select top 2 t2.*  from (
        select top 3 name,subject,score,stuid from t_stuscore where subject='数学' order by score desc
    ) t2 order by t2.score
) t3 order by t3.score desc


11．求出李四的数学成绩的排名


？？？

declare @tmp table(pm int,name varchar(50),score int,stuid int)
insert into @tmp select null,name,score,stuid from t_stuscore
where subject='数学' order by score desc
declare @id intset @id=0;
update @tmp set @id=@id+1,pm=@id select * from @tmp where name='李四';

12．统计如下：
课程
不及格（0-59）个
良（60-80）个
优（81-100）个






select subject,
(select count(*) from t_stuscore where score<60 and subject=t1.subject) as 不及格,
(select count(*) from t_stuscore where score between 60 and 80 and subject=t1.subject) as 良,
(select count(*) from t_stuscore where score >80 and subject=t1.subject) as 优
from t_stuscore t1 group by subject


13．统计如下：数学:张三(50分),李四(90分),王五(90分),赵六(76分)

？？？
declare @s varchar(1000)set @s=''
select @s =@s+','+name+'('+convert(varchar(10),score)+'分)'
from t_stuscore where subject='数学' set @s=stuff(@s,1,1,'') print '数学:'+@s