数据如下,我在答题过程中使用的是mysql数据库
create table Student
(
S varchar(10),
Sname nvarchar(10),
Sage datetime,
Ssex nvarchar(10)
);
insert into Student
values ('01', N'赵雷', '1990-01-01', N'男');
insert into Student
values ('02', N'钱电', '1990-12-21', N'男');
insert into Student
values ('03', N'孙风', '1990-05-20', N'男');
insert into Student
values ('04', N'李云', '1990-08-06', N'男');
insert into Student
values ('05', N'周梅', '1991-12-01', N'女');
insert into Student
values ('06', N'吴兰', '1992-03-01', N'女');
insert into Student
values ('07', N'郑竹', '1989-07-01', N'女');
insert into Student
values ('08', N'王菊', '1990-01-20', N'女');
create table Course
(
C varchar(10),
Cname nvarchar(10),
T varchar(10)
);
insert into Course
values ('01', N'语文', '02');
insert into Course
values ('02', N'数学', '01');
insert into Course
values ('03', N'英语', '03');
create table Teacher
(
T varchar(10),
Tname nvarchar(10)
);
insert into Teacher
values ('01', N'张三');
insert into Teacher
values ('02', N'李四');
insert into Teacher
values ('03', N'王五');
create table SC
(
S varchar(10),
C 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);
insert into SC
values ('07', '04', 98);
有些题目可能会有不对的sql,是在写题目的时候打得
# 1. 查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数
SELECT Student.S,Sname,Sage, Ssex,C,score_01,score_02
FROM Student
JOIN (
SELECT *
FROM (SELECT S,C,score score_01 FROM SC WHERE C = '01') a
LEFT JOIN (SELECT S new_s, C new_c, score score_02 FROM SC WHERE C = '02') b ON a.S = b.new_s
WHERE a.score_01 > b.score_02) c ON Student.S = c.new_s;
# 1.1 查询同时存在" 01 "课程和" 02 "课程的情况
SELECT *
FROM (SELECT * FROM SC WHERE C = '01') a
JOIN (SELECT * FROM SC WHERE C = '02') b ON a.S = b.S;
# 1.2 查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null )
SELECT *
FROM (SELECT * FROM SC WHERE C = '01') a
LEFT JOIN (SELECT * FROM SC WHERE C = '02') b ON a.S = b.S;
# 1.3 查询选课不存在" 01 "课程但存在" 02 "课程的情况
# 解法1
SELECT *
FROM SC
WHERE C = '02'
AND S NOT IN (SELECT S
FROM SC
WHERE C = '01');
# 解法2
SELECT *
FROM SC A
WHERE A.C = '02'
AND NOT EXISTS
(SELECT S
FROM SC B
WHERE A.S = B.S
AND C = '01');
# 解法3
SELECT *
FROM (SELECT * FROM SC WHERE C = '01') a
LEFT JOIN (SELECT * FROM SC WHERE C = '02') b ON a.S = b.S;
# 2. 查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩
SELECT A.S,B.Sname,A.dc
FROM (SELECT S,AVG(score) dc FROM SC GROUP BY S HAVING AVG(score) > 60) A
LEFT JOIN Student B ON A.S = B.S;
# 3. 查询在 SC 表存在成绩的学生信息
SELECT *
FROM Student
WHERE EXISTS(SELECT * FROM SC where SC.S = Student.S);
# 4. 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 Student.S, Student.Sname, 选课总数, 总成绩
FROM (SELECT S, count(C) 选课总数, sum(score) 总成绩 FROM SC GROUP BY S) A
RIGHT JOIN Student ON Student.S = A.S;
# 4.1 查有成绩的学生信息
SELECT Student.S, Student.Sname, 选课总数, 总成绩
FROM (SELECT S, count(C) 选课总数, sum(score) 总成绩 FROM SC GROUP BY S) A
LEFT JOIN Student ON Student.S = A.S;
# 5. 查询「李」姓老师的数量
SELECT COUNT(*)
FROM Teacher
where Tname LIKE '李%';
# 6. 查询学过「张三」老师授课的同学的信息
SELECT *
FROM Student
WHERE EXISTS(SELECT *
FROM SC
WHERE Student.S = SC.S
AND EXISTS(SELECT *
FROM Course
WHERE SC.C = Course.C
AND EXISTS(SELECT *
FROM Teacher
WHERE Teacher.Tname = '张三'
AND Course.T = Teacher.T)
));
# 7. 查询没有学全所有课程的同学的信息
# 解法1
SELECT *
FROM Student
WHERE S NOT IN (SELECT S FROM SC GROUP BY S HAVING COUNT(C) = (SELECT COUNT(*) FROM Course));
# 解法2
SELECT *
FROM Student
WHERE NOT EXISTS(
SELECT S
FROM SC
WHERE SC.S = Student.S
GROUP BY SC.S
HAVING COUNT(*) = (SELECT COUNT(*) FROM Course)
);
# 8. 查询至少有一门课与学号为" 01 "的同学所学相同的同学的信息
# 解法1
SELECT *
FROM Student
WHERE S IN (SELECT S
FROM SC
WHERE C IN (
SELECT DISTINCT C
FROM SC
WHERE S = '01'
));
# 解法2
SELECT *
FROM Student
WHERE EXISTS(
SELECT *
FROM SC A
WHERE A.S = Student.S
AND EXISTS(
SELECT *
FROM SC B
WHERE A.C = B.C
AND B.S = '01'
));
# 9. 查询和" 01 "号的同学学习的课程完全相同的其他同学的信息
# 解法1 先把找出选修了其他课程的人, 将其过滤, 然后分组统计
SELECT *
FROM Student C
WHERE EXISTS(
SELECT A.S
FROM SC A
WHERE C.S = A.S
AND EXISTS(SELECT * FROM SC B WHERE A.C = B.C AND B.S = '01')
GROUP BY A.S
HAVING COUNT(*) = (SELECT COUNT(*) FROM SC WHERE S = '01'));
SELECT *
FROM Student a
WHERE NOT EXISTS
(SELECT *
FROM SC b
WHERE S = '01'
AND NOT EXISTS
(SELECT * FROM SC c WHERE c.S = a.S AND c.C = b.C));
# 解法2
SELECT *
FROM Student
WHERE EXISTS(SELECT A.S
FROM SC A
JOIN (SELECT C FROM SC WHERE S = '01') B ON A.C = B.C
WHERE Student.S = A.S
GROUP BY A.S
HAVING COUNT(*) = (SELECT COUNT(*) FROM SC WHERE S = '01'));
# 10. 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 s
WHERE NOT EXISTS(
SELECT *
FROM SC sc
WHERE s.S = sc.S
AND EXISTS(
SELECT *
FROM Course c
WHERE sc.C = c.C
AND EXISTS(
SELECT *
FROM Teacher t
WHERE c.T = t.T
AND t.Tname = '张三'
)));
# 11. 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
WHERE EXISTS(SELECT S
FROM SC
WHERE Student.S = SC.S
GROUP BY S
HAVING SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) >= 2);
SELECT Student.S,Student.Sname,avg
FROM Student
JOIN (SELECT S,avg(score) avg
FROM SC
GROUP BY S
HAVING SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) >= 2) B ON Student.S = B.S;
# 12. 检索" 01 "课程分数小于 60学生信息,按分数降序排列的学生信息
SELECT *
FROM Student
JOIN (SELECT *
FROM SC
WHERE SC.score < 60
) B ON Student.S = B.S
ORDER BY score DESC;
# 13. 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 S,
MAX(CASE C WHEN '01' THEN score ELSE 0 END) '01',
MAX(CASE C WHEN '02' THEN score ELSE 0 END) '02',
MAX(CASE C WHEN '03' THEN score ELSE 0 END) '03',
AVG(score) 平均分
FROM SC
GROUP BY S
ORDER BY 平均分 DESC;
# 14. 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,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 ID,
Cname,
选修人数,
最高分,
最低分,
平均分,
及格率,
中等率,
优良率,
优秀率
FROM Course
JOIN (SELECT C ID,
COUNT(*) 选修人数,
MAX(score) 最高分,
MIN(score) 最低分,
AVG(score) 平均分,
SUM(CASE WHEN score >= 60 THEN 1 ELSE 0 END) / COUNT(*) * 100 及格率,
SUM(CASE WHEN score >= 70 AND score < 80 THEN 1 ELSE 0 END) / COUNT(*) * 100 中等率,
SUM(CASE WHEN score >= 80 AND score < 90 THEN 1 ELSE 0 END) / COUNT(*) * 100 优良率,
SUM(CASE WHEN score >= 90 THEN 1 ELSE 0 END) / COUNT(*) * 100 优秀率
FROM SC
GROUP BY C) A ON Course.C = A.ID
ORDER BY 选修人数 DESC,ID ASC;
# 15. 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 score,
CASE
WHEN @prevRank = score THEN ''
WHEN @prevRank := score THEN @curRank := @curRank + 1
END AS 排名
FROM SC,
(SELECT @curRank := 0,@prevRank := null) B
ORDER BY score DESC;
# 15.1 按各科成绩进行排序,并显示排名, Score 重复时合并名次
SELECT score,
CASE
WHEN @prevRank = score THEN @curRank
WHEN @prevRank := score THEN @curRank := @curRank + 1
END AS 排名
FROM SC,
(SELECT @curRank := 0,@prevRank := null) B
ORDER BY score DESC;
# 16. 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 S,
sum,
CASE
WHEN @prevRank = sum THEN ''
WHEN @prevRanK := sum Then @curRank := @curRank + 1
END AS PM
FROM (SELECT S,SUM(score) sum
FROM SC
GROUP BY S) A,
(SELECT @prevRank := NULL,@curRank := 0) B
ORDER BY sum DESC;
# 16.1 查询学生的总成绩,并进行排名,总分重复时不保留名次空
SELECT S,
sum,
CASE
WHEN @prevRank = sum THEN @curRank
WHEN @prevRanK := sum THEN @curRank := @curRank + 1
END AS PM
FROM (SELECT S,SUM(score) sum
FROM SC
GROUP BY S) A,
(SELECT @prevRank := NULL,@curRank := 0) B
ORDER BY sum DESC;
# 17. 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
SELECT *
FROM Course
JOIN
(SELECT C 课程编号,
SUM(CASE WHEN score < 100 AND score >= 85 THEN 1 ELSE 0 END) '[100-85]人数',
SUM(CASE WHEN score >= 70 THEN 1 ELSE 0 END) '[85-70]人数',
SUM(CASE WHEN score >= 60 THEN 1 ELSE 0 END) '[70-60]人数',
SUM(CASE WHEN score THEN 1 ELSE 0 END) '[60-0]人数',
SUM(CASE WHEN score < 100 AND score >= 85 THEN 1 ELSE 0 END) / COUNT(*) * 100 '[100-85]百分比',
SUM(CASE WHEN score >= 70 THEN 1 ELSE 0 END) / COUNT(*) * 100 '[85-70]百分比',
SUM(CASE WHEN score >= 60 THEN 1 ELSE 0 END) / COUNT(*) * 100 '[70-60]百分比',
SUM(CASE WHEN score THEN 1 ELSE 0 END) / COUNT(*) * 100 '[60-0]百分比'
FROM SC
GROUP BY C) b ON Course.C = b.课程编号;
# 18. 查询各科成绩前三名的记录
SELECT a.S,a.C,a.score
FROM SC a
LEFT JOIN SC b ON a.C = b.C AND a.score < b.score
GROUP BY a.S,a.C,a.score
HAVING COUNT(b.S) < 3
ORDER BY a.C,a.score DESC;
SELECT *
FROM SC a
WHERE (SELECT COUNT(DISTINCT score) FROM SC WHERE C = a.C AND score >= a.score) <= 3
ORDER BY a.C,a.score DESC;
# 19. 查询每门课程被选修的学生数
SELECT c, COUNT(*)
FROM SC
GROUP BY SC.C;
# 20. 查询出只选修两门课程的学生学号和姓名
SELECT Student.Sname,Student.S
FROM Student
WHERE (SELECT COUNT(*)
FROM SC
WHERE Student.S = SC.S
GROUP BY SC.S) = 2;
# 21. 查询男生、女生人数
SELECT Ssex,COUNT(*)
FROM Student
GROUP BY Ssex;
# 22. 查询名字中含有「风」字的学生信息
SELECT *
FROM Student
WHERE Sname LIKE '%风%';
# 23. 查询同名同性学生名单,并统计同名人数
SELECT Sname,Ssex,COUNT(*) 同名人数
FROM Student
GROUP BY Student.Sname,Ssex
HAVING COUNT(*) > 1;
# 24. 查询 1990 年出生的学生名单
SELECT *
FROM Student
WHERE YEAR(Sage) > 1990;
# 25. 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 C, AVG(SC.score) AVG
FROM SC
GROUP BY SC.C
ORDER BY AVG DESC,C ASC;
# 26. 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 Student.*,B.AVG
FROM Student
JOIN (SELECT S,AVG(score) AVG
FROM SC
GROUP BY SC.S
HAVING AVG >= 85) B ON Student.S = B.S;
# 27. 查询课程名称为「数学」,且分数低于 60 的学生姓名和分数
SELECT Student.*,B.score
FROM Student
JOIN (SELECT *
FROM SC
WHERE EXISTS(SELECT *
FROM Course
WHERE SC.C = Course.C
AND Cname = '数学')
AND score < 60) B ON Student.S = B.S;
# 28. 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 *
FROM Student
LEFT JOIN SC ON Student.S = SC.S;
# 29. 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 Student.Sname,Course.Cname,B.score
FROM Student
JOIN (SELECT *
FROM SC
WHERE SC.score > 70) B ON Student.S = B.S
JOIN Course ON B.C = Course.C;
# 30. 查询不及格的课程
SELECT *
FROM Course
WHERE EXISTS(SELECT *
FROM SC
WHERE Course.C = SC.C
AND score < 60);
# 31. 查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名
SELECT *
FROM Student
WHERE EXISTS(SELECT *
FROM SC
WHERE Student.S = SC.S
AND C = '01'
AND score = 80);
# 32. 求每门课程的学生人数
SELECT C,COUNT(*)
FROM SC
GROUP BY C;
# 33. 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 Student.*, B.score
FROM Student
JOIN (SELECT *
FROM SC
WHERE EXISTS(
SELECT *
FROM Course
WHERE SC.C = Course.C
AND EXISTS(SELECT *
FROM Teacher
WHERE Course.T = Teacher.T
AND Tname = '张三')
)
ORDER BY score DESC
LIMIT 1) B ON Student.S = B.S;
# 34. 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 SC a
WHERE EXISTS(
SELECT *
FROM Course
WHERE a.C = Course.C
AND EXISTS(SELECT *
FROM Teacher
WHERE Course.T = Teacher.T
AND Tname = '李四')
)
AND (SELECT COUNT(DISTINCT score) FROM SC WHERE C = a.C AND score > a.score) < 1
ORDER BY a.C,a.score DESC;
# 35. 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 SC A
, SC B
WHERE A.score = B.score
AND A.C != B.C
AND A.S != B.S;
# 36. 查询每门功成绩最好的前两名
SELECT *
FROM SC A
WHERE (SELECT COUNT(DISTINCT B.score)
FROM SC B
WHERE A.C = B.C
AND B.score > A.score) < 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)。
SELECT C
FROM SC
GROUP BY C
HAVING COUNT(*) > 5;
# 38. 检索至少选修两门课程的学生学号
SELECT S
FROM SC
GROUP BY S
HAVING COUNT(*) >= 2;
# 39. 查询选修了全部课程的学生信息
SELECT *
FROM Student
WHERE EXISTS(SELECT S
FROM SC
WHERE SC.S = Student.S
GROUP BY S
HAVING COUNT(*) = (SELECT COUNT(*) FROM Course));
SELECT *
FROM Student a
WHERE NOT EXISTS
(SELECT *
FROM SC b
WHERE S = '01'
AND NOT EXISTS
(SELECT * FROM SC c WHERE c.S = a.S AND c.C = b.C));
# 40. 查询各学生的年龄,只按年份来算
SELECT (YEAR(NOW()) - YEAR(Sage)) AGE
FROM Student;
# 41. 按照出生日期来算,当前月日 < 出生年月的月日则,年龄减一
SELECT if(DAY(NOW()) > DAY(Sage) AND MONTH(NOW()) > MONTH(Sage), (YEAR(NOW()) - YEAR(Sage)) - 1,
(YEAR(NOW()) - YEAR(Sage)))
FROM Student,
(SELECT @AGE := 0) B;
# 42. 查询本周过生日的学生
SELECT Student.*
FROM Student
WHERE WEEK(Sage) = WEEK(NOW());
# 43. 查询下周过生日的学生
SELECT Student.*
FROM Student
WHERE WEEK(Sage) = WEEK(NOW()) + 1;
# 44. 查询本月过生日的学生
SELECT *
FROM Student
WHERE MONTH(Student.Sage) = MONTH(NOW());
# 45. 查询下月过生日的学生
SELECT *
FROM Student
WHERE MONTH(Student.Sage) = MONTH(NOW()) + 1;