From 5b00fa2978d7e4eeac131e254bfdf68379ca3f38 Mon Sep 17 00:00:00 2001
From: fengzhao <fengzhao1124@hotmail.com>
Date: Thu, 10 Aug 2023 11:03:42 +0800
Subject: [PATCH] update sql practice

---
 docs/basic/6.sql_practice.md | 519 +++++++++++++++++++++++++++++++++++
 1 file changed, 519 insertions(+)

diff --git a/docs/basic/6.sql_practice.md b/docs/basic/6.sql_practice.md
index 68de88e86..2ee6574f7 100644
--- a/docs/basic/6.sql_practice.md
+++ b/docs/basic/6.sql_practice.md
@@ -258,3 +258,522 @@ SELECT e.ename, d.dname FROM emp e, dept d WHERE e.job =( SELECT job FROM emp WH
 33. 检索emp表，用is a 这个字符串来连接员工姓名和工种两个字段
 
 34. 检索emp表中有提成的员工姓名、月收入及提成。
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+```SQL
+
+-- DDL
+create table Student(sid varchar(10),sname varchar(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 varchar(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 varchar(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);
+
+-- 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
+
+-- 课程表
+-- Course(CId,Cname,TId)
+-- CId 课程编号,Cname 课程名称,TId 教师编号
+
+-- 教师表
+-- Teacher(TId,Tname)
+-- TId 教师编号,Tname 教师姓名
+
+-- 成绩表
+-- SC(SId,CId,score)
+-- SId 学生编号,CId 课程编号,score 分数
+
+-- 1. 查询“01”课程比“02”课程成绩高的所有学生的学号；
+select distinct t1.sid as sidfrom   
+    (select * from sc where cid='01')t1  
+left join   
+    (select * from sc where cid='02')t2  
+on t1.sid=t2.sid  
+where t1.score>t2.score
+
+-- 2. 查询平均成绩大于60分的同学的学号和平均成绩；
+select   
+    sid  
+    ,avg(score)  
+from sc  
+group by sid  
+having avg(score)>60
+
+-- 3. 查询所有同学的学号、姓名、选课数、总成绩
+select  
+    student.sid as sid  
+    ,sname  
+    ,count(distinct cid) course_cnt  
+    ,sum(score) as total_score  
+from student  
+left join sc  
+on student.sid=sc.sid  
+group by sid,sname
+
+-- 4. 查询姓“李”的老师的个数；
+select  
+    count(distinct tid) as teacher_cnt  
+from teacher  
+where tname like '李%'
+
+-- 5. 查询没学过“张三”老师课的同学的学号、姓名；
+select  
+    sid,sname  
+from student  
+where sid not in   
+    (  
+        select  
+            sc.sid  
+        from teacher  
+        left join course  
+            on teacher.tid=course.tid  
+        left join sc  
+            on course.cid=sc.cid  
+        where teacher.tname='张三'  
+    )
+
+-- 6. 查询学过“01”并且也学过编号“02”课程的同学的学号、姓名；
+select  
+    t.sid as sid  
+    ,sname  
+from   
+    (  
+        select  
+            sid  
+            ,count(if(cid='01',score,null)) as count1  
+            ,count(if(cid='02',score,null)) as count2  
+        from sc  
+        group by sid  
+        having count(if(cid='01',score,null))>0 and count(if(cid='02',score,null))>0  
+    )t  
+left join student  
+    on t.sid=student.sid
+
+-- 7. 查询学过“张三”老师所教的课的同学的学号、姓名；
+select  
+    student.sid  
+    ,sname  
+from   
+    (  
+        select  
+            distinct cid   
+        from course  
+        left join teacher   
+        on course.tid=teacher.tid  
+        where teacher.tname='张三'  
+    )course  
+left join sc   
+    on course.cid=sc.cid  
+left join student  
+    on sc.sid=student.sid  
+group by student.sid,sname
+
+-- 8. 查询课程编号“01”的成绩比课程编号“02”课程低的所有同学的学号、姓名；
+select  
+    t1.sid,sname  
+from   
+    (  
+        select distinct t1.sid as sid  
+        from   
+            (select * from sc where cid='01')t1  
+        left join   
+            (select * from sc where cid='02')t2  
+        on t1.sid=t2.sid  
+        where t1.score>t2.score  
+    )t1  
+left join student  
+    on t1.sid=student.sid
+
+-- 9. 查询所有课程成绩小于60分的同学的学号、姓名；
+select  
+    t1.sid,sname  
+from   
+    (  
+        select  
+            sid,max(score)  
+        from sc  
+        group by sid  
+        having max(score<60)  
+    )t1  
+left join student  
+    on t1.sid=student.sid
+
+-- 10. 查询没有学全所有课的同学的学号、姓名；
+select  
+    t1.sid,sname  
+from   
+    (  
+        select  
+            count(cid),sid  
+        from sc  
+        group by sid  
+        having count(cid) < (select count(distinct cid) from course)  
+    )t1  
+left join student  
+    on t1.sid=student.sid
+
+-- 11. 查询至少有一门课与学号为“01”的同学所学相同的同学的学号和姓名；
+select  
+    distinct sc.sid  
+from   
+    (  
+        select  
+            cid  
+        from sc  
+        where sid='01'  
+    )t1  
+left join sc  
+    on t1.cid=sc.cid
+
+-- 12. 查询和"01"号的同学学习的课程完全相同的其他同学的学号和姓名
+#注意是和'01'号同学课程完全相同但非学习课程数相同的,这里我用左连接解决这个问题select  
+    t1.sid,sname  
+from  
+    (  
+        select  
+            sc.sid  
+            ,count(distinct sc.cid)  
+        from   
+            (  
+                select  
+                    cid  
+                from sc  
+                where sid='01'  
+            )t1 #选出01的同学所学的课程  
+        left join sc  
+            on t1.cid=sc.cid  
+        group by sc.sid  
+        having count(distinct sc.cid)= (select count(distinct cid) from sc where sid = '01')  
+    )t1  
+left join student  
+    on t1.sid=student.sid  
+where t1.sid!='01'
+
+-- 13. 把“SC”表中“张三”老师教的课的成绩都更改为此课程的平均成绩；
+-- 暂跳过update题目
+
+
+-- 14. 查询没学过"张三"老师讲授的任一门课程的学生姓名
+select   
+    sname  
+from student  
+where sid not in  
+    (  
+        select  
+            distinct sid  
+        from sc  
+        left join course  
+            on sc.cid=course.cid  
+        left join teacher  
+            on course.tid=teacher.tid   
+        where tname='张三'  
+    )
+
+-- 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  
+    t1.sid,sname,avg_score  
+from   
+    (  
+        select  
+            sid,count(if(score<60,cid,null)),avg(score) as avg_score  
+        from sc  
+        group by sid  
+        having count(if(score<60,cid,null)) >=2  
+    )t1  
+left join student  
+    on t1.sid=student.sid
+
+-- 16. 检索"01"课程分数小于60，按分数降序排列的学生信息
+select   
+    sid,if(cid='01',score,100)from sc  
+where if(cid='01',score,100)<60  
+order by if(cid='01',score,100) desc
+
+-- 17. 按平均成绩从高到低显示所有学生的平均成绩
+select sid,avg(score)  
+from sc  
+group by sid  
+order by avg(score) desc
+
+-- 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
+select  
+    sc.cid  
+    ,cname  
+    ,max(score) as max_score  
+    ,min(score) as min_score  
+    ,avg(score) as avg_score  
+    ,count(if(score>=60,sid,null))/count(sid) as pass_rate  
+ from sc   
+ left join course  
+    on sc.cid=course.cid  
+ group by sc.cid
+
+-- 19. 按各科平均成绩从低到高和及格率的百分数从高到低顺序
+#这里先按照平均成绩排序，再按照及格百分数排序，  
+select   
+    cid  
+    ,avg(score) as avg_score  
+    ,count(if(score>=60,sid,null))/count(sid) as pass_rate  
+from sc  
+group by cid  
+order by avg_score,pass_rate desc
+
+-- 20. 查询学生的总成绩并进行排名
+select  
+    sid  
+    ,sum(score) as sum_score  
+from sc  
+group by sid  
+order by sum_score desc
+
+-- 21. 查询不同老师所教不同课程平均分从高到低显示
+select  
+    tid  
+    ,avg(score) as avg_score  
+from course  
+left join sc  
+    on course.cid=sc.cid  
+group by tid  
+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
+select  
+    sid,rank_num,score,cid  
+from  
+    (  
+        select  
+            rank() over(partition by cid order by score desc) as rank_num  
+            ,sid  
+            ,score  
+            ,cid  
+        from sc  
+    )t  
+where rank_num in (2,3)
+
+-- 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
+select  
+    sc.cid  
+    ,cname  
+    ,count(if(score between 85 and 100,sid,null))/count(sid)  
+    ,count(if(score between 70 and 85,sid,null))/count(sid)  
+    ,count(if(score between 60 and 70,sid,null))/count(sid)  
+    ,count(if(score between 0 and 60,sid,null))/count(sid)  
+from sc  
+left join course  
+    on sc.cid=course.cid  
+group by sc.cid,cname
+
+-- 24. 查询学生平均成绩及其名次
+select  
+    sid  
+    ,avg_score  
+    ,rank() over (order by avg_score desc)  
+from   
+    (  
+        select  
+            sid  
+            ,avg(score) as avg_score  
+        from sc  
+        group by sid  
+    )t
+
+-- 25. 查询各科成绩前三名的记录
+select  
+    sid,cid,rank1from   
+    (  
+        select  
+            cid  
+            ,sid  
+            ,rank() over(partition by cid order by score desc) as rank1  
+        from sc  
+    )twhere rank1<=3
+
+-- 26. 查询每门课程被选修的学生数
+select  
+    count(sid)  
+    ,cid  
+from sc  
+group by cid
+
+-- 27. 查询出只选修了一门课程的全部学生的学号
+select  
+    sid  
+from sc  
+group by sid  
+having count(cid) =1
+
+-- 28. 查询男生、女生人数
+select  
+    ssex  
+    ,count(distinct sid)  
+from student          
+group by ssex
+
+-- 29. 查询名字中含有"风"字的学生信息
+select  
+    sid,sname  
+from student  
+where sname like '%风%'
+
+-- 30. 查询同名同性学生名单，并统计同名人数
+select  
+    ssex  
+    ,sname  
+    ,count(sid)  
+from student  
+group by ssex,sname  
+having count(sid)>=2
+
+-- 31. 查询1990年出生的学生名单(注：Student表中Sage列的类型是datetime)
+select  
+    sid,sname,sage  
+from student  
+where year(sage)=1990
+
+-- 32. 查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列
+select  
+    cid,avg(score) as avg_score  
+from sc  
+group by cid  
+order by avg_score,cid desc
+
+-- 33. 查询不及格的课程，并按课程号从大到小排列
+select  
+    cid,sid,score  
+from sc  
+where score<60  
+order by cid desc,sid
+
+-- 34. 查询课程编号为"01"且课程成绩在60分以上的学生的学号和姓名；
+select  
+    sid,cid,score  
+from sc  
+where cid='01' and score>60
+
+-- 35. 查询选修“张三”老师所授课程的学生中，成绩最高的学生姓名及其成绩
+select  
+    sc.sid,sname,cname,score  
+from sc  
+left join course  
+    style="font-weight: 600;">=course.cid  
+left join teacher  
+    style="font-weight: 600;">=teacher.tid  
+left join student  
+    style="font-weight: 600;">=student.sid  
+where tname='张三'  
+order by score desc  
+limit 1;
+
+-- 36. 查询每门功课成绩最好的前两名
+select  
+    cid,sid,rank1  
+from   
+    (  
+        select  
+            cid  
+            ,sid  
+            ,rank() over(partition by cid order by score desc) as rank1  
+        from sc   
+    )t  
+where rank1 <=2
+
+-- 37. 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  
+    cid  
+    ,count(sid) as cnt  
+from sc  
+group by cid  
+having cnt>=5  
+order by count(sid) desc,cid
+
+-- 38. 检索至少选修两门课程的学生学号
+select  
+    sid  
+    ,count(cid)  
+from sc  
+group by sid  
+having count(cid)>=2
+
+-- 39. 查询选修了全部课程的学生信息
+select  
+    sid  
+    ,count(cid)  
+from sc  
+group by sid  
+having count(cid)=(select count(distinct cid) from sc)
+
+-- 40. 查询各学生的年龄
+select  
+    sid,sname,year(curdate())-year(sage) as sage  
+from student
+
+-- 41. 查询本周过生日的学生
+select  
+    sid,sname,sage  
+from student  
+where weekofyear(sage)=weekofyear(curdate())
+
+-- 42. 查询下周过生日的学生
+select   
+    sid,sname,sage  
+from student  
+where weekofyear(sage) = weekofyear(date_add(curdate(),interval 1 week))
+
+-- 43 查询本月过生日的学生
+select  
+    sid,sname,sage  
+from student  
+where month(sage) = month(curdate())
+
+-- 44. 查询下月过生日的学生
+select  
+    sid,sname,sage  
+from student  
+where month(date_sub(sage,interval 1 month)) = month(curdate())