mysql查询语句举例

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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

2. 问题：

计算每个人的总成绩并排名，并按总成绩降序排列(要求显示字段：学号，姓名，总成绩)
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)
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)
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)
列出各门课程的平均成绩，并按平均成绩降序排列（要求显示字段：课程，平均成绩）
列出总分成绩的排名（要求显示字段：学号，姓名，成绩，排名）
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）
求出李四的数学成绩的排名
统计如下：

学号	姓名	语文	数学	英语	总分	平均分

10. 统计如下：

课程	不及格（0-59）个	良（60-80）个	优（81-100）个

3. 参考答案

select stuid, name, sum(score) as sum_score from stuscore group by stuid order by sum_score desc;
select stuid, name, sub, score from stuscore where score in (select max(score) from stuscore group by stuid);
select stuid, name, sub, score from stuscore where score in (select max(score) from stuscore group by sub);
select a.* from stuscore a where exists (select count(*) from stuscore where sub = a.sub and score > a.score having count(*) < 2) order by
a.sub, a.score desc;
select sub, avg(score) as avg_score from stuscore group by sub order by avg_score desc;
select (select
(count(stuid)+1 from (select stuid, sum(score) as sum_score from stuscore group by stuid)
as A where A.sum_score > B.sum_score) as seq,
B.stuid, B.name, B.sum_score from (select stuid, name, sum(score) as sum_score from stuscore group by stuid) as
B order by sum_score desc;
select stuid, name, score, sub from stuscore where sub = 'math' order by score desc limit 1, 3;
select (select
(count(stuid)+1 from (select stuid, score from stuscore where sub = 'math')
as A where A.score > B.score) as seq,
B.stuid, B.name, B.sum_score from (select stuid, name, sub, score from stuscore where sub = 'math' and name = '李四') as
B;
select stuid, name, sum(case when sub = 'chinese' then score else 0 end) as chinese, sum(case when sub = 'math' then score else 0 end) as math, sum(case when sub = 'english' then score else 0 end)
as english, sum(score) as sum_score, avg(score) as avg_score from stuscore group by stuid;
select sub, sum(case when score < 60 then 1 else 0 end) as lower_60, sum(case when score < 81 and score > 59 then 1 else 0 end) as between_60_80, sum(case when score > 80 then 1 else 0 end) as
higher_80 from stuscore group by sub;