sql统计查询实例代码
本文导语: 首先,创建用到的数据表。 代码示例: CREATE TABLE `stuscore` ( `id` int(11) NOT NULL auto_increment, `name` varchar(20) default NULL, `subject` varchar(20) default NULL, `score` varchar(20) default NULL, `stuid` varchar(10) default NUL...
首先,创建用到的数据表。
`id` int(11) NOT NULL auto_increment,
`name` varchar(20) default NULL,
`subject` varchar(20) default NULL,
`score` varchar(20) default NULL,
`stuid` varchar(10) default NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
然后,添加测试数据。
insert into `stuscore`(`id`,`name`,`subject`,`score`,`stuid`) values
(1,'张三','数学','89','1'),
(2,'张三','语文','80','1'),
(3,'张三','英语','70','1'),
(4,'李四','数学','90','2'),
(5,'李四','语文','70','2'),
(6,'李四','英语','80','2');
#--问题及解答:
1. 计算每个人的总成绩并排名(要求显示字段:姓名,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)
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 stuid,max(score) as maxscore from stuscore group by stuid) t2
where t1.stuid=t2.stuid and t1.score=t2.maxscore
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,avg(score) as avgscore from 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 subject,max(score) as maxscore from 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 top 2 stuscore.stuid from stuscore where subject = t1.subject order by score desc)
order by t1.subject
该语句未测试,目前知道在mysql下无法运行。mysql不支持select top。
7.
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 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 stuscore group by subject
9. 列出数学成绩的排名(要求显示字段:学号,姓名,成绩,排名)
不知道我自己想法对不对?
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 top 2 t2.* from (
select top 3 name,subject,score,stuid from 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
insert into @tmp select null,name,score,stuid from stuscore where subject='数学' order by score desc
declare @id int
set @id=0;
update @tmp set @id=@id+1,pm=@id
select * from @tmp where name='李四'
12.
(select count(*) from stuscore where score80 and subject=t1.subject) as 优
from 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)
set @s=''
select @s =@s+','+name+'('+convert(varchar(10),score)+'分)' from stuscore where subject='数学'
set @s=stuff(@s,1,1,'')
print '数学:'+@s
说:第10,11,13题未验证,大家在使用时,注意测试。