一：表与数据
CREATE DATABASE db01;
USE db01;
-- 学生表 student
CREATE TABLE student(Sid VARCHAR(10),Sname NVARCHAR(10),Sage DATETIME,Ssex NVARCHAR(10))
INSERT INTO student VALUES('01' , N'赵雷' , '1990-01-01' , N'男'),
('02' , N'钱电' , '1990-12-21' , N'男'),
('03' , N'孙风' , '1990-05-20' , N'男'),
('04' , N'李云' , '1990-08-06' , N'男'),
('05' , N'周梅' , '1991-12-01' , N'女'),
('06' , N'吴兰' , '1992-03-01' , N'女'),
('07' , N'郑竹' , '1989-07-01' , N'女'),
('08' , N'王菊' , '1990-01-20' , N'女');
-- 科目表 course
CREATE TABLE course(Cid VARCHAR(10),Cname NVARCHAR(10),Tid VARCHAR(10))
INSERT INTO course VALUES('01' , N'语文' , '02'),('02' , N'数学' , '01'),('03' , N'英语' , '03');
-- 教师表 teacher
CREATE TABLE teacher(Tid VARCHAR(10),Tname NVARCHAR(10))
INSERT INTO teacher VALUES('01' , N'张三'),('02' , N'李四'),('03' , N'王五');
-- 成绩表 sc
CREATE TABLE sc(Sid VARCHAR(10),Cid VARCHAR(10),score DECIMAL(18,1))
INSERT INTO sc VALUES('01' , '01' , 80)
,('01' , '02' , 90)
,('01' , '03' , 99)
,('02' , '01' , 70)
,('02' , '02' , 60)
,('02' , '03' , 80)
,('03' , '01' , 80)
,('03' , '02' , 80)
,('03' , '03' , 80)
,('04' , '01' , 50)
,('04' , '02' , 30)
,('04' , '03' , 20)
,('05' , '01' , 76)
,('05' , '02' , 87)
,('06' , '01' , 31)
,('06' , '03' , 34)
,('07' , '02' , 89)
,('07' , '03' , 98);
二练习题：
-- 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 a.Sid,a.score,student.* FROM (SELECT * FROM sc WHERE sc.`Cid`=01 ) a
LEFT JOIN (SELECT * FROM sc WHERE sc.cid=02)b ON a.Sid=b.Sid
LEFT JOIN student ON a.Sid=student.Sid
WHERE a.score>b.score;
-- 1.1 查询同时存在" 01 "课程和" 02 "课程的情况
SELECT * FROM (SELECT * FROM sc WHERE sc.`Cid`=01) a
INNER JOIN (SELECT * FROM sc WHERE sc.`Cid`=02) b
ON a.Sid=b.Sid;
-- 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 sc.`Cid`=01) a
LEFT JOIN (SELECT * FROM sc WHERE sc.`Cid`=02) b
ON a.Sid=b.Sid;
-- 1.3 查询不存在" 01 "课程但存在" 02 "课程的情况
SELECT b.* FROM
(SELECT * FROM sc WHERE sc.`Cid`=02) b
LEFT JOIN
(SELECT * FROM sc WHERE sc.`Cid`=01) a
ON b.Sid=a.Sid
WHERE a.Sid IS NULL;
-- 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 * FROM student stu
INNER JOIN
(SELECT sc.Sid,AVG(score) AS avgscore FROM sc GROUP BY Sid) a
ON stu.`Sid`=a.Sid
WHERE a.avgscore > 60
-- 3. 查询在 sc 表存在成绩的学生信息
SELECT * FROM
sc LEFT JOIN
student stu
ON sc.`Sid`=stu.`Sid`
WHERE sc.`score` IS NOT NULL;
-- 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 * FROM student stu
LEFT JOIN
(SELECT Sid,COUNT(Cid),SUM(score) FROM sc GROUP BY Sid) b
ON stu.`Sid`=b.Sid
-- 4.1 查有成绩的学生信息
SELECT DISTINCT stu.Sname,stu.`Sage`,stu.`Ssex`
FROM sc
LEFT JOIN student stu ON stu.`Sid`=sc.`Sid`
WHERE sc.`score` IS NOT NULL;
-- 5. 查询「李」姓老师的数量
SELECT COUNT(*) '「李」姓老师的数量'
FROM teacher
WHERE Tname LIKE '李四%'
-- 6. 查询学过「张三」老师授课的同学的信息
SELECT * FROM student stu
WHERE stu.Sid IN
(SELECT Sid FROM course
LEFT JOIN sc
ON course.`Cid`=sc.`Cid`
WHERE course.Tid
IN(SELECT Tid FROM teacher
WHERE teacher.`Tname`='张三'))
-- 7. 查询没有学全所有课程的同学的信息
SELECT * FROM student stu
WHERE stu.Sid IN (SELECT stu.Sid FROM student stu
LEFT JOIN sc
ON stu.Sid=sc.Sid
WHERE sc.`Cid` IS NULL)
-- 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
#1
SELECT * FROM student stu
WHERE stu.Sid IN (SELECT DISTINCT sc.Sid FROM sc
WHERE sc.`Cid` IN (SELECT course.Cid FROM course
WHERE course.`Cid` IN (SELECT sc.`Cid` FROM sc
WHERE sc.Sid=01)))
#2
SELECT * FROM student WHERE Sid IN (SELECT Sid FROM sc WHERE Cid IN (SELECT Cid FROM sc WHERE Sid = '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
#01号同学的课程
SELECT sc.`Cid` FROM sc
WHERE sc.`Sid`=01
#02不在以上课程中的同学
SELECT sc.`Sid` FROM sc
WHERE sc.`Cid` NOT IN (SELECT sc.`Cid` FROM sc
WHERE sc.`Sid`=01)
#数据02子集的同学
SELECT * FROM sc
WHERE sc.`Sid` NOT IN(
SELECT sc.`Sid` FROM sc
WHERE sc.`Cid` NOT IN (SELECT sc.`Cid` FROM sc
WHERE sc.`Sid`=01)
);
#痛过grouby将所有数据按照sid进行分组，并计算出每组的sid数量
SELECT DISTINCT sc.Sid FROM sc
WHERE sc.Sid IN(
SELECT sc.Sid FROM sc
WHERE sc.`Sid` NOT IN(
SELECT sc.`Sid` FROM sc
WHERE sc.`Cid` NOT IN (SELECT sc.`Cid` FROM sc
WHERE sc.`Sid`=01))
GROUP BY Sid
HAVING COUNT(*)=(SELECT COUNT(*) FROM sc WHERE sc.`Sid`=01) AND sc.Sid!=01);
#查上面所查到的sid的信息
SELECT * FROM student
WHERE student.`Sid` IN (
SELECT DISTINCT sc.Sid FROM sc
WHERE sc.Sid IN(
SELECT sc.Sid FROM sc
WHERE sc.`Sid` NOT IN(
SELECT sc.`Sid` FROM sc
WHERE sc.`Cid` NOT IN (SELECT sc.`Cid` FROM sc
WHERE sc.`Sid`=01))
GROUP BY Sid
HAVING COUNT(*)=(SELECT COUNT(*) FROM sc WHERE sc.`Sid`=01) AND sc.Sid!=01));
-- 10. 查询没学过"张三"老师讲授的任一门课程的学生姓名
EXPLAIN SELECT * FROM (SELECT DISTINCT Sid FROM sc
WHERE sc.`Sid` NOT IN (SELECT Cid FROM course c
LEFT JOIN teacher t
ON c.`Tid`=t.`Tid`
WHERE t.`Tname`='张三')) mx LEFT JOIN student
ON mx.Sid=student.`Sid`
EXPLAIN SELECT SQL_NO_CACHE * FROM student
WHERE student.Sid IN (SELECT DISTINCT Sid FROM sc
WHERE sc.`Sid` NOT IN (SELECT Cid FROM course c
LEFT JOIN teacher t
ON c.`Tid`=t.`Tid`
WHERE t.`Tname`='张三'));
CREATE INDEX sc_index IN sc
-- 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
#1查询两门以上不及格的sid和平均值
SELECT sc.`Sid`,AVG(score) FROM sc
WHERE sc.`score` < 60
GROUP BY sc.`Sid`
HAVING COUNT(*) >=2
#2联表student
SELECT a.score,a.Sid,stu.Sname FROM (SELECT sc.`Sid`,AVG(score) score FROM sc
WHERE sc.`score` < 60
GROUP BY sc.`Sid`
HAVING COUNT(*) >=2) a
LEFT JOIN student stu
ON a.Sid = stu.Sid
-- 12. 检索" 01 "课程分数小于 60，按分数降序排列的学生信息
SELECT * FROM (SELECT * FROM sc
WHERE sc.`Cid`=01 AND sc.`score` < 60) a
LEFT JOIN student stu
ON a.`Sid`=stu.Sid
ORDER BY a.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 DISTINCT sc.`Sid`,a.av FROM sc
LEFT JOIN (SELECT Sid,AVG(sc.`score`) av FROM sc
GROUP BY sc.`Sid`) a
ON sc.`Sid`=a.Sid
ORDER BY a.av
-- 14. 查询各科成绩最高分、最低分和平均分：
SELECT * FROM course cou
LEFT JOIN (SELECT sc.`Cid`,MAX(score),MIN(score),AVG(score) FROM sc
GROUP BY sc.`Cid`) b
ON cou.Cid=b.Cid
-- 15. 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
#01将各分数线分类
SELECT
CASE WHEN score >= 60 AND score < 70 THEN '及格'
WHEN score >= 70 AND score < 80 THEN '中等'
WHEN score >= 80 AND score < 90 THEN '优良'
WHEN score >= 90 THEN '优秀'
ELSE '不及格'
END grade
FROM sc
#02进入主题
SELECT * FROM course a
LEFT JOIN(SELECT Cid,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(DISTINCT Sid) AS '及格率',
SUM(CASE WHEN score >= 70 AND score < 80 THEN 1 ELSE 0 END ) / COUNT(DISTINCT Sid) '中等率',
SUM(CASE WHEN score >= 80 AND score < 90 THEN 1 ELSE 0 END ) / COUNT(DISTINCT Sid) '优良率',
SUM(CASE WHEN score >= 90 THEN 1 ELSE 0 END ) / COUNT(DISTINCT Sid) '优秀率'
FROM sc
GROUP BY Cid) b
ON a.Cid=b.Cid
-- 16. 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 sc.`Cid`,COUNT(*) FROM sc
GROUP BY sc.`Cid`
ORDER BY COUNT(*) DESC,sc.`Cid` 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
#同score为null
SET @rk=0;
SET @last_Cid=0;
SET @score=0;
SELECT sc.`Cid`,sc.`score`,sc.`Sid`,IF(@last_Cid=sc.`Cid`,
IF(@score=sc.`score`,NULL,@rk:=@rk+1),
@rk:=1) AS rk,
@last_Cid:=sc.`Cid` AS last_Cid,
@score:=sc.`score` AS last_score
FROM sc
ORDER BY sc.`Cid`,sc.`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(1,1,2,3,4...)
#同分数并列排名，所有自定义变量都要打印，否则结果会是错的
SET @rk=0;
SET @last_Cid=0;
SET @score=0;
SELECT sc.`Cid`,sc.`score`,sc.`Sid`,IF(@id=sc.`Cid`,
IF(@score=sc.`score`,@rk:=@rk,@rk:=@rk+1),
@rk:=1) AS rk,
@id:=sc.`Cid` AS id,
@score:=sc.`score` AS last_score
FROM sc
ORDER BY sc.`Cid`,sc.`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 sc.`Sid`,SUM(sc.`score`) sumscore FROM sc
GROUP BY sc.`Sid`
ORDER BY sumscore
-- 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缺
-- 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] 及所占百分比
#01
SELECT sc.`Cid`,
SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[60-0]',
SUM(CASE WHEN score >= 60 AND score < 70 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[70-60]',
SUM(CASE WHEN score >= 70 AND score < 85 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[85-70]',
SUM(CASE WHEN score >= 85 AND score < 100 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[100-85]'
FROM sc
GROUP BY sc.`Cid`;
#02联表查询
SELECT * FROM course a
LEFT JOIN (SELECT sc.`Cid`,
SUM(CASE WHEN score < 60 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[60-0]',
SUM(CASE WHEN score >= 60 AND score < 70 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[70-60]',
SUM(CASE WHEN score >= 70 AND score < 85 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[85-70]',
SUM(CASE WHEN score >= 85 AND score < 100 THEN 1 ELSE 0 END) / COUNT(DISTINCT Sid) '[100-85]'
FROM sc
GROUP BY sc.`Cid`) b
ON a.Cid=b.Cid;
-- 18. 查询各科成绩前三名的记录 使用自定义函数
SET @rank=0;
SET @last_Cid=0;
SELECT a.Cid,a.Sid,a.score,a.rk FROM (SELECT Cid,Sid,score,
IF(@last_Cid=Cid,@rank:=@rank+1,@rank:=1) AS rk,
@last_Cid:=Cid
FROM sc
ORDER BY sc.`Cid`,sc.`score` DESC) a
WHERE a.rk <=3
-- 19. 查询每门课程被选修的学生数
SELECT sc.`Cid`,COUNT(sc.`Sid`) FROM sc
GROUP BY sc.`Cid`
-- 20. 查询出只选修两门课程的学生学号和姓名
SELECT * FROM student a
WHERE a.Sid IN (SELECT sc.`Sid` FROM sc
GROUP BY sc.`Sid`
HAVING COUNT(DISTINCT sc.`Cid`)=2)
-- 21. 查询男生、女生人数
#1
SELECT
SUM(CASE WHEN Ssex='男' THEN 1 ELSE 0 END) '男',
SUM(CASE WHEN Ssex='女' THEN 1 ELSE 0 END) '女'
FROM student
#2
SELECT st.Ssex,COUNT(*) FROM student st
GROUP BY st.Ssex
-- 22. 查询名字中含有「风」字的学生信息
SELECT * FROM student stu
WHERE stu.Sname LIKE '%风%'
-- 23. 查询同名同性学生名单，并统计同名人数
#1
SELECT a.Sname, a.Ssex,COUNT(*) FROM student a
GROUP BY a.Sname, a.Ssex
HAVING COUNT(*)>= 2
#2
SELECT c.Sname,c.Ssex, COUNT(DISTINCT c.Sid) AS counts FROM (
SELECT a.Sid, a.Sname, a.Ssex FROM student a
INNER JOIN student b
ON a.Sname = b.Sname
AND a.Ssex = b.Ssex
) c
GROUP BY c.Sname, c.Ssex
HAVING COUNT(c.Sid) >= 2;
-- 24. 查询 1990 年出生的学生名单
SELECT * FROM student stu
WHERE YEAR(stu.`Sage`)='1990' AND MONTH(stu.Sage)='05'
-- 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 sc.`Cid`,AVG(score) FROM sc
GROUP BY sc.`Cid`
ORDER BY AVG(score) DESC,sc.`Cid` 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
#01查询每名同学的平均成绩
SELECT Sid,AVG(sc.`score`) FROM sc
GROUP BY sc.`Sid`
#02进入正题
SELECT * FROM student a
INNER JOIN(SELECT Sid,AVG(sc.`score`) FROM sc
GROUP BY sc.`Sid`
HAVING AVG(sc.`score`) > 85 ) b
ON a.`Sid`=b.Sid
-- 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 b.Sname,sc.`score` FROM course a
LEFT JOIN sc
ON a.Cid=sc.`Cid`
LEFT JOIN student b
ON SC.`Sid`=b.Sid
WHERE a.Cname='数学' AND sc.`score`<60
-- 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 a.Sname,COUNT(*) '课程数量',IF(AVG(b.`score`),AVG(b.`score`),0) FROM student a
LEFT JOIN sc b
ON a.Sid=b.Sid
GROUP BY a.Sname
SELECT a.*, b.* FROM student a
LEFT JOIN sc b
ON a.Sid = b.Sid;
-- 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 b.`Sname`,c.`Cname`,a.score FROM
(SELECT * FROM sc
WHERE sc.`score` > 70) a
LEFT JOIN student b
ON a.`Sid`=b.Sid
LEFT JOIN course c
ON a.Cid=c.`Cid`
-- 30. 查询不及格的课程
SELECT a.Sid,c.Sname,b.Cname,a.Score FROM sc a
LEFT JOIN course b
ON a.Cid=b.Cid
LEFT JOIN student c
ON a.Sid=c.Sid
WHERE a.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 a.Sid,b.Sname FROM student a
LEFT JOIN sc b
ON a.Sid=b.`Sid`
WHERE b.`Cid`=01 AND b.`score`>80
-- 32. 求每门课程的学生人数
SELECT Cid,COUNT(DISTINCT Sid) FROM sc a
GROUP BY a.`Cid`;
-- 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
#1
SELECT d.*,e.score FROM student d
LEFT JOIN(SELECT DISTINCT c.Sid,c.`score` FROM course a
LEFT JOIN teacher b
ON a.`Tid`=b.`Tid`
LEFT JOIN sc c
ON a.Cid=c.Cid
WHERE b.`Tname`='张三') e
ON d.Sid=e.Sid
ORDER BY e.score DESC
LIMIT 1
#2
SELECT * FROM (
SELECT a.Sid, MAX(a.score) AS maxscore, b.Sname, rank() over(ORDER BY a.score DESC) AS rk FROM sc a
LEFT JOIN student b
ON a.Sid = b.Sid
WHERE Cid = (
SELECT Cid FROM course WHERE Tid = (SELECT Tid FROM teacher WHERE Tname = '张三'))
GROUP BY Sid)c
WHERE c.rk = 1;
-- 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 (
SELECT a.Sid, MAX(a.score) AS maxscore, b.Sname,dense_rank() over(ORDER BY a.score DESC) AS rk FROM sc a
LEFT JOIN student b
ON a.Sid = b.Sid
WHERE Cid = (
SELECT Cid FROM course WHERE Tid = (SELECT Tid FROM teacher WHERE Tname = '张三'))
GROUP BY Sid)c
WHERE c.rk = 1;
-- 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 DISTINCT d.`Sname`,c.`Cname`,a.`score` FROM sc a
INNER JOIN sc b
ON a.`score`=b.`score` AND a.`Cid`!=b.`Cid`
LEFT JOIN course c
ON b.`Cid`=c.`Cid`
INNER JOIN student d
ON b.Sid=d.Sid
-- 36. 查询每门功课成绩最好的前两名
#1排序错的，未查找到原因
SET @rank=0;
SET @last_Cid=0;
SELECT *,
IF (@last_Cid=b.`Cid`,@rank:=@rank+1,@rank:=1) AS rk,
@last_Cid:=b.`Cid` AS last_Cid
FROM course2 a
LEFT JOIN sc2 b
ON a.`Cid`=b.`Cid`
ORDER BY b.Cid,b.`score` DESC
#正确的方式
SELECT a.Sid,b.Sname,a.`Cid` FROM(SELECT sc.`Cid`,sc.`score`,sc.`Sid`,
IF(@id=sc.`Cid`,@rk:=@rk+1,@rk:=1) AS rk,
@id:=sc.`Cid` AS id
FROM sc
ORDER BY sc.`Cid`,sc.`score` DESC) a
LEFT JOIN student b
ON a.Sid=b.Sid
WHERE a.rk <=2
#下面同score为null
SET @rk=0;
SET @last_Cid=0;
SET @score=0;
SELECT sc.`Cid`,sc.`score`,sc.`Sid`,IF(@last_Cid=sc.`Cid`,
IF(@score=sc.`score`,null,@rk:=@rk+1),
@rk:=1) AS rk,
@last_Cid:=sc.`Cid` AS last_Cid,
@score:=sc.`score` AS last_score
FROM sc
ORDER BY sc.`Cid`,sc.`score` DESC
#同分数并列排名，所有自定义变量都要打印，否则结果会是错的
SET @rk=0;
SET @last_Cid=0;
SET @score=0;
SELECT sc.`Cid`,sc.`score`,sc.`Sid`,IF(@id=sc.`Cid`,
IF(@score=sc.`score`,@rk:=@rk,@rk:=@rk+1),
@rk:=1) AS rk,
@id:=sc.`Cid` AS id,
@score:=sc.`score` AS last_score
FROM sc
ORDER BY sc.`Cid`,sc.`score` DESC
-- 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 sc.`Cid`,COUNT(*) FROM sc
GROUP BY sc.`Cid`
HAVING COUNT(sc.`Sid`)>5
-- 38. 检索至少选修两门课程的学生学号
SELECT sc.`Sid`,COUNT(DISTINCT sc.`Cid`) FROM sc
GROUP BY sc.`Sid`
HAVING COUNT(DISTINCT sc.`Cid`) >= 2
-- 39. 查询选修了全部课程的学生信息
SELECT * FROM sc a
LEFT JOIN student b
ON a.Sid=b.`Sid`
GROUP BY a.`Sid`
HAVING COUNT(DISTINCT a.`Cid`)=(SELECT COUNT(DISTINCT Cid) FROM sc )
-- 40. 查询各学生的年龄，只按年份来算
SELECT (YEAR(CURDATE()) - YEAR(student.Sage) + 1) 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 student.`Sid`,IF(YEAR(CURDATE()) < YEAR(student.Sage),(YEAR(CURDATE()) - YEAR(student.Sage) - 1),(YEAR(CURDATE()) - YEAR(student.Sage) + 1)) AS '年龄' FROM student;
-- 42. 查询本周过生日的学生
SELECT stu.`Sid`,stu.`Sname` FROM student stu
WHERE WEEK(stu.`Sage`)=WEEK(NOW());
-- 43. 查询下周过生日的学生
SELECT stu.`Sid`,stu.`Sname` FROM student stu
WHERE WEEK(stu.`Sage`)=WEEK(NOW())+1;
-- 44. 查询本月过生日的学生
SELECT stu.`Sid`,stu.`Sname` FROM student stu
WHERE MONTH(stu.`Sage`)=MONTH(NOW());
-- 45. 查询下月过生日的学生
SELECT stu.`Sid`,stu.`Sname` FROM student stu
WHERE MONTH(stu.`Sage`)=MONTH(NOW())+1;
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