Mysql-进阶--地狱级查询语句

数据库脚本

因为数据的特殊性，请勿随意修改本人数据，内藏玄机。可随意增加，查询数据

-- 1. 创建学生表
CREATE TABLE t_student (
	sid INT NOT NULL AUTO_INCREMENT COMMENT '学号',
	sname VARCHAR(40) NOT NULL COMMENT '名称',
	birthday DATE NOT NULL COMMENT '年龄',
	ssex TINYINT NOT NULL DEFAULT 1 COMMENT '1男，2女',
	PRIMARY KEY (sid)
);
-- 添加学生表的数据
INSERT INTO t_student VALUES(1, '赵雷' , '1990-01-01' , 1);
INSERT INTO t_student VALUES(2 , '钱电' , '1990-12-21' , 1);
INSERT INTO t_student VALUES(3 , '孙风' , '1990-12-20' , 1);
INSERT INTO t_student VALUES(4 , '李云' , '1990-12-06' , 1);
INSERT INTO t_student VALUES(5 , '周梅' , '1991-12-01' , 2);
INSERT INTO t_student VALUES(6 , '吴兰' , '1992-01-01' , 2);
INSERT INTO t_student VALUES(7 , '郑竹' , '1989-01-01' , 2);
INSERT INTO t_student VALUES(9 , '张三' , '2017-12-20' , 2);
INSERT INTO t_student VALUES(10 , '李四' , '2017-12-25' , 2);
INSERT INTO t_student VALUES(11 , '李四' , '2012-06-06' , 2);
INSERT INTO t_student VALUES(12 , '赵六' , '2013-06-13' , 2);
INSERT INTO t_student VALUES(13 , '孙七' , '2014-06-01' , 2);
-- 2.创建教师表
CREATE TABLE t_teacher (
	tid INT NOT NULL AUTO_INCREMENT COMMENT '教师ID',
	tname VARCHAR(40) NOT NULL COMMENT '教师名称',
	PRIMARY KEY (tid)
-- 主键
);
-- 添加教师表数据
INSERT INTO t_teacher VALUES(1 , '张五哥');
INSERT INTO t_teacher VALUES(2 , '李卫');
INSERT INTO t_teacher VALUES(3 , '年羹尧');
-- 3.课程表
CREATE TABLE t_course (
	cid INT NOT NULL COMMENT '课程ID',
	cname VARCHAR(50) COMMENT '课程名称',
	tid INT COMMENT '教师id',
	PRIMARY KEY (cid)
);
-- 添加数据
INSERT INTO t_course VALUES(1 , '语文' , 2);
INSERT INTO t_course VALUES(2 , '数学' , 1);
INSERT INTO t_course VALUES(3 , '英语' , 3);

-- 4.成绩表
CREATE TABLE t_score (
	sid INT NOT NULL COMMENT '学号，外键',
	cid INT NOT NULL COMMENT '课程id',
	score decimal(5,2) COMMENT '成绩',
	UNIQUE KEY ak_key_sid_cid (sid, cid)
);

-- 添加数据
INSERT INTO t_score VALUES(1 , 1 , 80);
INSERT INTO t_score VALUES(1 , 2 , 90);
INSERT INTO t_score VALUES(1 , 3 , 99);
INSERT INTO t_score VALUES(2 , 1 , 70);
INSERT INTO t_score VALUES(2 , 2 , 60);
INSERT INTO t_score VALUES(2 , 3 , 80);
INSERT INTO t_score VALUES(3 , 1 , 80);
INSERT INTO t_score VALUES(3 , 2 , 80);
INSERT INTO t_score VALUES(3 , 3 , 80);
INSERT INTO t_score VALUES(4 , 1 , 50);
INSERT INTO t_score VALUES(4 , 2 , 30);
INSERT INTO t_score VALUES(4 , 3 , 20);
INSERT INTO t_score VALUES(5 , 1 , 76);
INSERT INTO t_score VALUES(5 , 2 , 87);
INSERT INTO t_score VALUES(6 , 1 , 31);
INSERT INTO t_score VALUES(6 , 3 , 34);
INSERT INTO t_score VALUES(7 , 2 , 89);
INSERT INTO t_score VALUES(7 , 3 , 98);

01）查询" 1 "课程比" 2 "课程成绩高的学生的信息及课程分数

SELECT stu.sid,stu.sname,stu.ssex,c1.cid, c1.score, c2.cid, c2.score
FROM t_student stu
INNER JOIN  (SELECT t1.sid, t1.cid, t1.score FROM t_score t1 WHERE t1.cid = 1 ) c1
ON stu.sid = c1.sid
INNER JOIN  (SELECT t2.sid, t2.cid, t2.score FROM t_score t2 WHERE t2.cid = 2) c2
ON stu.sid = c2.sid 
WHERE c1.score > c2.score

02）查询同时存在" 01 "课程和" 02 "课程的情况

select * from t_student stu 
INNER JOIN
(select c1.sid ,c1.cid c1id,c2.cid c2cid  from 
(select * from t_score where cid =1) c1
INNER JOIN
(select * from t_score where cid =2) c2
on c1.sid=c2.sid) cc
on cc.sid=stu.sid

03）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 t.sid, 
	sum(case when t.cid=1 then t.score else 0 end), 
	sum(case when t.cid=2 then t.score else null end) 
from t_score t GROUP BY t.sid
 

04）查询不存在" 01 "课程但存在" 02 "课程的情况

SELECT t1.sid,t1.cid,t1.score 
FROM t_score t1 
WHERE t1.cid = 2 AND t1.sid NOT IN (SELECT t2.sid FROM t_score t2 WHERE t2.cid = 1); 

05）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 aa.sid,st.*,aa.s1 
from t_student st
INNER JOIN
(select * from (
select sid,avg(score) s1 from t_score GROUP BY sid ) t where t.s1 >= 60) aa
on aa.sid=st.sid

06）查询在t_score表存在成绩的学生信息

1.select * from t_student t where exists (select * from t_score ts where ts.sid=t.sid)

2.select DISTINCT stu.sid,stu.sname,stu.birthday from t_score t INNER JOIN (select * from t_student) stu on t.sid=stu.sid  

07）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 stu.sid,stu.sname,stu.* ,count(cid) ccid,
		sum(case when cid=1 then score else 0 end) c1,
		sum(case when cid=1 then score else 0 end) c2, 
		sum(case when cid=1 then score else 0 end) c3 
from t_student stu
left JOIN
t_score sco 
on sco.sid=stu.sid GROUP BY sid

08）查询「李」姓老师的数量

select count(tid) from t_teacher where tname like '李%';

09）查询学过「张三」老师授课的同学的信息

SELECT t1.sid,t1.sname,t1.ssex, t4.tid, t4.tname
FROM t_student t1 
       INNER JOIN t_score t2 ON t1.sid=t2.sid
       INNER JOIN t_course t3 ON t2.cid = t3.cid
       INNER JOIN t_teacher t4 ON t3.tid = t4.tid
WHERE t4.tname = '李卫';

10）查询没有学全所有课程的同学的信息

select * from 
(select stu.sid,stu.sname,stu.birthday,stu.ssex,aa.sid aasid from t_student stu
left JOIN 
(select a.sid from (select sid,count(*) ccid from t_score GROUP BY sid) a where a.ccid=3)aa
on stu.sid=aa.sid ) cc where cc.aasid is null

11）查询没学过"张三"老师讲授的任一门课程的学生姓名

SELECT t1.sid, t1.sname,t4.tname
FROM t_student t1 
     LEFT JOIN t_score t2 ON t1.sid=t2.sid 
     LEFT JOIN t_course t3 ON t2.cid=t3.cid
     LEFT JOIN t_teacher t4 ON t3.tid = t4.tid
WHERE t4.tname != '李卫' OR t4.tname IS NULL;

12）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 aa.sid,aa.sname,avg(case when aa.score is null then 0 else aa.score end) 
from (select stu.sid,stu.sname,sco.score from t_student stu 
LEFT JOIN 
t_score sco 
on sco.sid=stu.sid 
where score<60 or score is null) aa GROUP BY sid

14）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 stu.sid,stu.sname,
		sum(case when sco.cid=1 then sco.score else 0 end) '语文',
		sum(case when sco.cid=2 then sco.score else 0 end) '数学',
		sum(case when sco.cid=3 then sco.score else 0 end) '英语',
		avg(case when sco.score is null then 0 else sco.score end) aa
from t_student stu
left JOIN
t_score sco on sco.sid=stu.sid GROUP BY stu.sid ORDER BY aa desc

15）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 t2.cid '课程ID', 
       t2.cname '课程名称',
       MAX(t1.score) '最高分',
       MIN(t1.score) '最低分',
       ROUND(AVG(t1.score), 2) '平均分',
       COUNT(t1.sid) '选修人数',
       ROUND(SUM(CASE WHEN t1.score >= 60 THEN 1 ELSE 0 END) / COUNT(t1.sid), 2) '及格率',
       ROUND(SUM(CASE WHEN t1.score >=70 AND t1.score < 80 THEN 1 ELSE 0 END)/COUNT(t1.sid),2) '中等率',
       ROUND(SUM(CASE WHEN t1.score >=80 AND t1.score < 90 THEN 1 ELSE 0 END)/COUNT(t1.sid),2) '优良率',
       ROUND(SUM(CASE WHEN t1.score >= 90 THEN 1 ELSE 0 END)/COUNT(t1.sid), 2) '优秀率'
 FROM t_score t1
      INNER JOIN t_course t2 ON t1.cid = t2.cid
GROUP BY t2.cid, t2.cname
ORDER BY COUNT(t1.sid) DESC, t2.cid ASC;