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+```sql
+2023年10月20 日
+
+ 1 -- 1. 查询" 1 "课程比" 2 "课程成绩高的学生的信息（学号、姓名、性别、出生日期）及课程分数
+
+
+-- 2. 查询同时参与" 1 "课程和" 2 "课程考试的学生信息
+SELECT * from (
+SELECT * from student  where  student_id in (SELECT student_id from score where course_id =1 or course_id=2 GROUP BY student_id HAVING COUNT(*)>1))a left join score b on a.student_id=b.student_id; 
+ 3 -- 3. 查询存在" 1 "课程但可能不存在" 2 "课程的情况(不存在时显示为 null )
+
+
+-- 4. 查询不存在" 1 "课程但存在" 2 "课程的情况
+SELECT * from score where student_id not in (
+SELECT student_id from score where course_id=1);
+-- 5. 查询平均成绩大于等于 60 分的同学的学生编号、姓名和平均成绩
+SELECT a.student_id , student_name,AVG(score) from student a JOIN score b on a.student_id= b.student_id GROUP BY a.student_id HAVING AVG(score)>=60;
+
+SELECT student_id ,student_name from student where student_id in ( SELECT student_id from score GROUP BY student_id HAVING AVG(score>=60));
+-- 6. 查询在成绩表存在成绩的学生信息
+SELECT * from student where student_id in (
+SELECT student_id from score );
+
+ 7 -- 7. 查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )
+SELECT 
+DISTINCT
+  a.student_id , 
+    student_name ,
+    COUNT(course_id) over (partition by a.student_id )'选课总数'
+     from student a JOIN score b on a.student_id = b.student_id   ; 
+-- 8. 查询「李」姓老师的数量
+SELECT COUNT(*) from teacher where teacher_name like '李%';
+-- 9. 查询学过「李白」老师授课的同学的信息
+SELECT * from student where student_id IN (
+SELECT student_id from score where course_id   = (
+SELECT course_id from course where teacher_id   =(
+SELECT teacher_id from teacher where teacher_name   = "李白")));
+-- 10. 查询没有学全所有课程的同学的信息
+SELECT * from student where student_id not in (
+SELECT student_id from score where course_id =1 OR course_id =2 OR   course_id =3);
+ 11 -- 11. 查询至少有一门课与学号为" 1 "的同学所学相同的同学的信息
+SELECT * from student where student_id in (
+SELECT student_id from score  where course_id in (
+SELECT course_id from score where student_id =1 ));
+12  -- 12. 查询和" 1 "号的同学学习的课程完全相同的其他同学的信息
+
+-- 13. 查询没学过「李白」老师讲授的任一门课程的学生姓名
+SELECT * from student where student_id not in (
+SELECT student_id from score where course_id in (
+SELECT course_id  from course where teacher_id in(
+SELECT teacher_id from teacher where teacher_name = '李白')));
+-- 14. 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 * from student st, (
+SELECT student_id ,count(*)a from score where score<60 GROUP BY student_id having a>=2 )c where st.student_id =c.student_id;
+
+-- 15. 检索" 1 "课程分数小于 60，按分数降序排列的学生信息
+SELECT * from student a join score b on a.student_id=b.student_id where b.course_id=1 and b.score <60 ORDER BY b.score desc;
+-- 16. 按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩
+SELECT student_id ,course_id, score ,avg(score ) over (partition by student_id ) 平均成绩
+from score order by  平均成绩 desc;
+-- 17. 查询各科成绩最高分、最低分和平均分
+SELECT MAX(score),min(score),AVG(score) from score ;
+-- 18. 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，中等率，优良率，优秀率（及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90），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 course_name , X.* from course,(
+SELECT 
+course_id,
+count(*) 人数,
+MAX(score),
+MIN(score),
+AVG(score),
+sum( (case when score >=90 and score<= 100 then 1 end ))/ count(*) 优秀率,
+sum( (case when score >=80 and score< 90 then 1 end ))/ count(*) 优良率,
+sum( (case when score >=70 and score< 80 then 1 end ))/ count(*) 中等率,
+sum( (case when score >=0 and score< 60 then 1 end ))/ count(*) 及格率
+from score group by course_id ) X where X.course_id=course.course_id order by 人数 desc , course_id asc;
+-- 19. 按各科成绩进行排序，并显示排名，Score 重复时保留名次空缺
+SELECT course_id 科目,score 成绩,RANK() over(PARTITION by course_id ORDER BY score)排名 FROM score;
+
+-- 20. 按各科成绩进行排序，并显示排名，Score 重复时合并名次
+SELECT course_id,score,DENSE_RANK() over(PARTITION by course_id ORDER BY score) FROM score;
+
+-- 21. 查询学生的总成绩，并进行排名，总分重复时保留名次空缺
+SELECT 总成绩 , RANK() over (ORDER BY 总成绩) from 
+(SELECT sum(score) 总成绩 from score GROUP BY student_id ) b;
+
+-- 22. 查询学生的总成绩，并进行排名，总分重复时不保留名次空缺
+SELECT 总成绩 , dense_rank() over (order by 总成绩 ) from 
+(SELECT sum(score) 总成绩 from score GROUP BY student_id )b;
+-- 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]，[60-0] 及所占百分比
+SELECT course_name,A.* FROM course,(
+SELECT 
+course_id,
+count(*) 人数,
+sum((CASE WHEN score>=85 and score<=100 THEN 1 END)) `[100-85]`,
+sum((CASE WHEN score>=70 and score<85 THEN 1 END)) `[85-70]`,
+sum((CASE WHEN score>=60 and score<70 THEN 1 END)) `[70-60]`,
+sum((CASE WHEN score>=0 and score<60 THEN 1 END)) `[60-0]`,
+sum((CASE WHEN score>=85 and score<=100 THEN 1 END))/count(*),
+sum((CASE WHEN score>=70 and score<85 THEN 1 END))/count(*),
+sum((CASE WHEN score>=60 and score<75 THEN 1 END))/count(*),
+sum((CASE WHEN score>=0 and score<60 THEN 1 END))/count(*)
+ FROM score GROUP BY course_id) A WHERE A.course_id=course.course_id;
+-- 24. 查询各科成绩前三名的记录
+SELECT * FROM (
+SELECT *,rank() over(PARTITION by course_id ORDER BY score desc) 排名 FROM score ) a WHERE 排名<=3
+-- 25. 查询每门课程被选修的学生数
+SELECT * , count(student_id) over (PARTITION by course_id) from score ;
+-- 26. 查询出只选修两门课程的学生学号和姓名
+SELECT * from student s,( 
+SELECT student_id ,count(course_id ) 选修 from score GROUP BY student_id having 选修 = 2) a where s.student_id = a.student_id;
+-- 27. 查询男生、女生人数
+SELECT  gender ,COUNT(*) from student GROUP BY gender;
+-- 28. 查询名字中含有「风」字的学生信息
+SELECT * FROM student WHERE student_name like '%风%';
+-- 29. 查询同名同性学生名单，并统计同名人数
+SELECT count(*) FROM student a,student b WHERE a.student_name=b.student_name and a.gender=b.gender and a.student_id!=b.student_id;
+-- 30. 查询 1990 年出生的学生名单
+SELECT * FROM student WHERE year(birthday) = 1990;
+-- 31. 查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列
+SELECT avg(score) 平均成绩 FROM score GROUP BY course_id ORDER BY 平均成绩 desc,course_id asc;
+-- 32. 查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩
+SELECT* from student s, ( 
+SELECT student_id ,avg(score) 平均成绩 from score GROUP BY student_id having 平均成绩>=85 ) a where s.student_id =a.student_id;
+-- 33. 查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
+SELECT * FROM student WHERE student_id in(
+SELECT student_id FROM score WHERE course_id=(
+SELECT course_id FROM course WHERE course_name='数学') and score<60);
+-- 34. 查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）
+SELECT DISTINCT * FROM student s LEFT JOIN score on s.student_id=score.student_id LEFT JOIN course on score.course_id=course.course_id;
+-- 35. 查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数
+SELECT * FROM student s1,(
+SELECT student_id,score,course_id FROM score WHERE score>70) a,course c WHERE s1.student_id=a.student_id and c.course_id=a.course_id;
+-- 36. 查询不及格的课程
+SELECT * FROM score WHERE score<60;
+-- 37. 查询课程编号为 1 且课程成绩在 80 分以上的学生的学号和姓名
+SELECT * FROM student WHERE student_id in (
+SELECT student_id FROM score WHERE score>80 and course_id=1);
+-- 38. 求每门课程的学生人数
+SELECT count(*) FROM score GROUP BY course_id;
+-- 39. 成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩
+SELECT * FROM student s1,score s2 WHERE s1.student_id=s2.student_id and score=(
+SELECT max(score) FROM score WHERE course_id=(
+SELECT DISTINCT course_id FROM course WHERE teacher_id=(
+SELECT teacher_id FROM teacher WHERE teacher_name='张三')));
+-- 40. 成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩
+SELECT * FROM student s1,score s2 WHERE s1.student_id=s2.student_id and score=(
+SELECT max(score) FROM score WHERE course_id=(
+SELECT course_id FROM course WHERE teacher_id=(
+SELECT teacher_id FROM teacher WHERE teacher_name='张三')));
+-- 41. 查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩
+SELECT * FROM student s1,score s2 WHERE s1.student_id=s2.student_id and s1.student_id in (
+SELECT a.student_id FROM score a,score b WHERE a.student_id=b.student_id and a.score=b.score and a.course_id!=b.course_id);
+-- 42. 查询每门功成绩最好的前两名
+with a as (
+SELECT student_id,course_id,rank() over(PARTITION by course_id ORDER BY score) 排名 FROM score)
+SELECT * FROM a WHERE 排名<=2;
+-- 43. 统计每门课程的学生选修人数（超过 5 人的课程才统计）。
+SELECT course_id,count(*) 选修人数 FROM score GROUP BY course_id HAVING 选修人数 >5
+-- 44. 检索至少选修两门课程的学生学号
+SELECT student_id,count(course_id) 选修 FROM score GROUP BY student_id HAVING 选修 >=2;
+-- 45. 查询选修了全部课程的学生信息
+SELECT * FROM student s,( 
+SELECT student_id,count(course_id) 课程 FROM score GROUP BY student_id HAVING 课程=(SELECT count(*) FROM course)) a WHERE s.student_id=a.student_id;
+-- 46. 查询各学生的年龄，只按年份来算
+SELECT student_name,year(NOW())-year(birthday) 年龄  FROM student;
+-- 47. 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一
+
+-- 48. 查询本周过生日的学生
+with a as (
+SELECT WEEK(birthday,1),student_name 生日周 FROM student)
+SELECT * FROM a WHERE a.生日周=(SELECT week(NOW(),1));
+
+-- 49. 查询下周过生日的学生
+with a as (
+SELECT WEEK(birthday,1),student_name 生日周 FROM student)
+SELECT * FROM a WHERE a.生日周=(SELECT week(NOW(),1)+1);
+
+-- 50. 查询本月过生日的学生
+with a as (
+SELECT student_name,MONTH(birthday) 生日月 FROM student)
+SELECT * FROM a WHERE 生日月=month(NOW());
+-- 51. 查询下月过生日的学生
+with a as (
+SELECT student_name,MONTH(birthday) 生日月 FROM student)
+SELECT * FROM a WHERE 生日月=month(NOW()+1);
+```
+