--建表
--學生表
CREATE TABLE `Student`(
`s_id` VARCHAR(20),
`s_name` VARCHAR(20) NOT NULL DEFAULT '',
`s_birth` VARCHAR(20) NOT NULL DEFAULT '',
`s_sex` VARCHAR(10) NOT NULL DEFAULT '',
PRIMARY KEY(`s_id`)
);
--課程表
CREATE TABLE `Course`(
`c_id` VARCHAR(20),
`c_name` VARCHAR(20) NOT NULL DEFAULT '',
`t_id` VARCHAR(20) NOT NULL,
PRIMARY KEY(`c_id`)
);
--教師表
CREATE TABLE `Teacher`(
`t_id` VARCHAR(20),
`t_name` VARCHAR(20) NOT NULL DEFAULT '',
PRIMARY KEY(`t_id`)
);
--成績表
CREATE TABLE `Score`(
`s_id` VARCHAR(20),
`c_id` VARCHAR(20),
`s_score` INT(3),
PRIMARY KEY(`s_id`,`c_id`)
);
--插入學生表測試數(shù)據(jù)
insert into Student values('01' , '趙雷' , '1990-01-01' , '男');
insert into Student values('02' , '錢電' , '1990-12-21' , '男');
insert into Student values('03' , '孫風' , '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' , '吳蘭' , '1992-03-01' , '女');
insert into Student values('07' , '鄭竹' , '1989-07-01' , '女');
insert into Student values('08' , '王菊' , '1990-01-20' , '女');
--課程表測試數(shù)據(jù)
insert into Course values('01' , '語文' , '02');
insert into Course values('02' , '數(shù)學' , '01');
insert into Course values('03' , '英語' , '03');

--教師表測試數(shù)據(jù)
insert into Teacher values('01' , '張三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');

--成績表測試數(shù)據(jù)
insert into Score values('01' , '01' , 80);
insert into Score values('01' , '02' , 90);
insert into Score values('01' , '03' , 99);
insert into Score values('02' , '01' , 70);
insert into Score values('02' , '02' , 60);
insert into Score values('02' , '03' , 80);
insert into Score values('03' , '01' , 80);
insert into Score values('03' , '02' , 80);
insert into Score values('03' , '03' , 80);
insert into Score values('04' , '01' , 50);
insert into Score values('04' , '02' , 30);
insert into Score values('04' , '03' , 20);
insert into Score values('05' , '01' , 76);
insert into Score values('05' , '02' , 87);
insert into Score values('06' , '01' , 31);
insert into Score values('06' , '03' , 34);
insert into Score values('07' , '02' , 89);
insert into Score values('07' , '03' , 98);

-- 準備條件,去掉 sql_mode 的 ONLY_FULL_GROUP_BY 否則此種情況下會報錯:
-- Expression #1 of select list is not in group by clause and contains nonaggregated column 'userinfo.
-- 原因：
-- MySQL 5.7.5和up實現(xiàn)了對功能依賴的檢測。如果啟用了only_full_group_by SQL模式(在默認情況下是這樣)，
-- 那么MySQL就會拒絕選擇列表、條件或順序列表引用的查詢，這些查詢將引用組中未命名的非聚合列，而不是在功能上依賴于它們。
-- (在5.7.5之前，MySQL沒有檢測到功能依賴項，only_full_group_by在默認情況下是不啟用的。關于前5.7.5行為的描述，請參閱MySQL 5.6參考手冊。)
-- 執(zhí)行以下個命令，可以查看 sql_mode 的內容。
SHOW SESSION VARIABLES;
SHOW GLOBAL VARIABLES;
select @@sql_mode;
-- 更改
set global sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
set session sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';

-- 1、查詢"01"課程比"02"課程成績高的學生的信息及課程分數(shù) 
select st.*,sc.s_score as '語文' ,sc2.s_score '數(shù)學' 
from student st
left join score sc on sc.s_id=st.s_id and sc.c_id='01' 
left join score sc2 on sc2.s_id=st.s_id and sc2.c_id='02' 
where sc.s_score>sc2.s_score

-- 2、查詢"01"課程比"02"課程成績低的學生的信息及課程分數(shù)
select st.*,sc.s_score '語文',sc2.s_score '數(shù)學' from student st
left join score sc on sc.s_id=st.s_id and sc.c_id='01'
left join score sc2 on sc2.s_id=st.s_id and sc2.c_id='02'
where sc.s_score<sc2.s_score

-- 3、查詢平均成績大于等于60分的同學的學生編號和學生姓名和平均成績
select st.s_id,st.s_name,ROUND(AVG(sc.s_score),2) cjScore from student st
left join score sc on sc.s_id=st.s_id
group by st.s_id having AVG(sc.s_score)>=60

-- 4、查詢平均成績小于60分的同學的學生編號和學生姓名和平均成績
  -- (包括有成績的和無成績的)
select st.s_id,st.s_name,(case when ROUND(AVG(sc.s_score),2) is null then 0 else ROUND(AVG(sc.s_score)) end ) cjScore from student st
left join score sc on sc.s_id=st.s_id
group by st.s_id having AVG(sc.s_score)<60 or AVG(sc.s_score) is NULL

-- 5、查詢所有同學的學生編號、學生姓名、選課總數(shù)、所有課程的總成績
select st.s_id,st.s_name,count(c.c_id),( case when SUM(sc.s_score) is null or sum(sc.s_score)="" then 0 else SUM(sc.s_score) end) from student st
left join score sc on sc.s_id =st.s_id 
left join course c on c.c_id=sc.c_id
group by st.s_id

-- 6、查詢"李"姓老師的數(shù)量 
select t.t_name,count(t.t_id) from teacher t
group by t.t_id having t.t_name like "李%"; 

-- 7、查詢學過"張三"老師授課的同學的信息 
select st.* from student st 
left join score sc on sc.s_id=st.s_id
left join course c on c.c_id=sc.c_id
left join teacher t on t.t_id=c.t_id
 where t.t_name="張三"

-- 8、查詢沒學過"張三"老師授課的同學的信息 
 -- 張三老師教的課
 select c.* from course c left join teacher t on t.t_id=c.t_id where t.t_name="張三"
 -- 有張三老師課成績的st.s_id
 select sc.s_id from score sc where sc.c_id in (select c.c_id from course c left join teacher t on t.t_id=c.t_id where t.t_name="張三")
 -- 不在上面查到的st.s_id的學生信息,即沒學過張三老師授課的同學信息
 select st.* from student st where st.s_id not in(
 select sc.s_id from score sc where sc.c_id in (select c.c_id from course c left join teacher t on t.t_id=c.t_id where t.t_name="張三")
 )

-- 9、查詢學過編號為"01"并且也學過編號為"02"的課程的同學的信息
select st.* from student st 
inner join score sc on sc.s_id = st.s_id
inner join course c on c.c_id=sc.c_id and c.c_id="01"
where st.s_id in (
select st2.s_id from student st2 
inner join score sc2 on sc2.s_id = st2.s_id
inner join course c2 on c2.c_id=sc2.c_id and c2.c_id="02"
)


網(wǎng)友提供的思路(厲害呦~):
SELECT st.*
FROM student st
INNER JOIN score sc ON sc.`s_id`=st.`s_id`
GROUP BY st.`s_id`
HAVING SUM(IF(sc.`c_id`="01" OR sc.`c_id`="02" ,1,0))>1

-- 10、查詢學過編號為"01"但是沒有學過編號為"02"的課程的同學的信息
select st.* from student st 
inner join score sc on sc.s_id = st.s_id
inner join course c on c.c_id=sc.c_id and c.c_id="01"
where st.s_id not in (
select st2.s_id from student st2 
inner join score sc2 on sc2.s_id = st2.s_id
inner join course c2 on c2.c_id=sc2.c_id and c2.c_id="02"
)

-- 11、查詢沒有學全所有課程的同學的信息
 -- 太復雜,下次換一種思路,看有沒有簡單點方法
 -- 此處思路為查學全所有課程的學生id,再內聯(lián)取反面
select * from student where s_id not in (
select st.s_id from student st 
inner join score sc on sc.s_id = st.s_id and sc.c_id="01"
where st.s_id in (
select st2.s_id from student st2 
inner join score sc2 on sc2.s_id = st2.s_id and sc2.c_id="02"
) and st.s_id in (
select st2.s_id from student st2 
inner join score sc2 on sc2.s_id = st2.s_id and sc2.c_id="03"
))
-- 來自一樓網(wǎng)友的思路，左連接，根據(jù)學生id分組過濾掉 數(shù)量小于 課程表中總課程數(shù)量的結果(show me his code),簡潔不少。
select st.* from Student st
left join Score S
on st.s_id = S.s_id
group by st.s_id
having count(c_id)<(select count(c_id) from Course)





-- 12、查詢至少有一門課與學號為"01"的同學所學相同的同學的信息
select distinct st.* from student st 
left join score sc on sc.s_id=st.s_id
where sc.c_id in (
select sc2.c_id from student st2
left join score sc2 on sc2.s_id=st2.s_id
where st2.s_id ='01'
)

-- 13、查詢和"01"號的同學學習的課程完全相同的其他同學的信息
select st.* from student st 
left join score sc on sc.s_id=st.s_id
group by st.s_id
having group_concat(sc.c_id) = 
(
select group_concat(sc2.c_id) from student st2
left join score sc2 on sc2.s_id=st2.s_id
where st2.s_id ='01'
)

-- 14、查詢沒學過"張三"老師講授的任一門課程的學生姓名
select st.s_name from student st 
where st.s_id not in (
select sc.s_id from score sc 
inner join course c on c.c_id=sc.c_id
inner join teacher t on t.t_id=c.t_id and t.t_name="張三"
)

-- 15、查詢兩門及其以上不及格課程的同學的學號，姓名及其平均成績
select st.s_id,st.s_name,avg(sc.s_score) from student st
left join score sc on sc.s_id=st.s_id
where sc.s_id in (
select sc.s_id from score sc 
where sc.s_score<60 or sc.s_score is NULL
group by sc.s_id having COUNT(sc.s_id)>=2
)
group by st.s_id

-- 16、檢索"01"課程分數(shù)小于60，按分數(shù)降序排列的學生信息
select st.*,sc.s_score from student st 
inner join score sc on sc.s_id=st.s_id and sc.c_id="01" and sc.s_score<60
order by sc.s_score desc

-- 17、按平均成績從高到低顯示所有學生的所有課程的成績以及平均成績
 -- 可加round,case when then else end 使顯示更完美
select st.s_id,st.s_name,avg(sc4.s_score) "平均分",sc.s_score "語文",sc2.s_score "數(shù)學",sc3.s_score "英語" from student st
left join score sc on sc.s_id=st.s_id and sc.c_id="01"
left join score sc2 on sc2.s_id=st.s_id and sc2.c_id="02"
left join score sc3 on sc3.s_id=st.s_id and sc3.c_id="03"
left join score sc4 on sc4.s_id=st.s_id
group by st.s_id 
order by SUM(sc4.s_score) desc

-- 18.查詢各科成績最高分、最低分和平均分：以如下形式顯示：課程ID，課程name，最高分，最低分，平均分，及格率，中等率，優(yōu)良率，優(yōu)秀率
-- 及格為>=60，中等為：70-80，優(yōu)良為：80-90，優(yōu)秀為：>=90
select c.c_id,c.c_name,max(sc.s_score) "最高分",MIN(sc2.s_score) "最低分",avg(sc3.s_score) "平均分" 
,((select count(s_id) from score where s_score>=60 and c_id=c.c_id )/(select count(s_id) from score where c_id=c.c_id)) "及格率"
,((select count(s_id) from score where s_score>=70 and s_score<80 and c_id=c.c_id )/(select count(s_id) from score where c_id=c.c_id)) "中等率"
,((select count(s_id) from score where s_score>=80 and s_score<90 and c_id=c.c_id )/(select count(s_id) from score where c_id=c.c_id)) "優(yōu)良率"
,((select count(s_id) from score where s_score>=90 and c_id=c.c_id )/(select count(s_id) from score where c_id=c.c_id)) "優(yōu)秀率"
from course c
left join score sc on sc.c_id=c.c_id 
left join score sc2 on sc2.c_id=c.c_id 
left join score sc3 on sc3.c_id=c.c_id 
group by c.c_id

-- 19、按各科成績進行排序，并顯示排名(實現(xiàn)不完全)
-- mysql沒有rank函數(shù)
-- 加@score是為了防止用union all 后打亂了順序
select c1.s_id,c1.c_id,c1.c_name,@score:=c1.s_score,@i:=@i+1 from (select c.c_name,sc.* from course c 
left join score sc on sc.c_id=c.c_id
where c.c_id="01" order by sc.s_score desc) c1 ,
(select @i:=0) a
union all 
select c2.s_id,c2.c_id,c2.c_name,c2.s_score,@ii:=@ii+1 from (select c.c_name,sc.* from course c 
left join score sc on sc.c_id=c.c_id
where c.c_id="02" order by sc.s_score desc) c2 ,
(select @ii:=0) aa 
union all
select c3.s_id,c3.c_id,c3.c_name,c3.s_score,@iii:=@iii+1 from (select c.c_name,sc.* from course c 
left join score sc on sc.c_id=c.c_id
where c.c_id="03" order by sc.s_score desc) c3;
set @iii=0;


-- 20、查詢學生的總成績并進行排名
select st.s_id,st.s_name
,(case when sum(sc.s_score) is null then 0 else sum(sc.s_score) end)
 from student st
left join score sc on sc.s_id=st.s_id
group by st.s_id order by sum(sc.s_score) desc

-- 21、查詢不同老師所教不同課程平均分從高到低顯示 
select t.t_id,t.t_name,c.c_name,avg(sc.s_score) from teacher t 
left join course c on c.t_id=t.t_id 
left join score sc on sc.c_id =c.c_id
group by t.t_id
order by avg(sc.s_score) desc

-- 22、查詢所有課程的成績第2名到第3名的學生信息及該課程成績
select a.* from (
select st.*,c.c_id,c.c_name,sc.s_score from student st
left join score sc on sc.s_id=st.s_id
inner join course c on c.c_id =sc.c_id and c.c_id="01"
order by sc.s_score desc LIMIT 1,2 ) a
union all
select b.* from (
select st.*,c.c_id,c.c_name,sc.s_score from student st
left join score sc on sc.s_id=st.s_id
inner join course c on c.c_id =sc.c_id and c.c_id="02"
order by sc.s_score desc LIMIT 1,2) b
union all
select c.* from (
select st.*,c.c_id,c.c_name,sc.s_score from student st
left join score sc on sc.s_id=st.s_id
inner join course c on c.c_id =sc.c_id and c.c_id="03"
order by sc.s_score desc LIMIT 1,2) c

-- 23、統(tǒng)計各科成績各分數(shù)段人數(shù)：課程編號,課程名稱,[100-85],[85-70],[70-60],[0-60]及所占百分比
select c.c_id,c.c_name 
,((select count(1) from score sc where sc.c_id=c.c_id and sc.s_score<=100 and sc.s_score>80)/(select count(1) from score sc where sc.c_id=c.c_id )) "100-85"
,((select count(1) from score sc where sc.c_id=c.c_id and sc.s_score<=85 and sc.s_score>70)/(select count(1) from score sc where sc.c_id=c.c_id )) "85-70"
,((select count(1) from score sc where sc.c_id=c.c_id and sc.s_score<=70 and sc.s_score>60)/(select count(1) from score sc where sc.c_id=c.c_id )) "70-60"
,((select count(1) from score sc where sc.c_id=c.c_id and sc.s_score<=60 and sc.s_score>=0)/(select count(1) from score sc where sc.c_id=c.c_id )) "60-0"
from course c order by c.c_id

-- 24、查詢學生平均成績及其名次 
set @i=0;
select a.*,@i:=@i+1 from (
select st.s_id,st.s_name,round((case when avg(sc.s_score) is null then 0 else avg(sc.s_score) end),2) "平均分" from student st
left join score sc on sc.s_id=st.s_id
group by st.s_id order by sc.s_score desc) a

-- 25、查詢各科成績前三名的記錄
select a.* from (
 select st.s_id,st.s_name,c.c_id,c.c_name,sc.s_score from student st
 left join score sc on sc.s_id=st.s_id
 inner join course c on c.c_id=sc.c_id and c.c_id='01'
 order by sc.s_score desc LIMIT 0,3) a
union all 
select b.* from (
 select st.s_id,st.s_name,c.c_id,c.c_name,sc.s_score from student st
 left join score sc on sc.s_id=st.s_id
 inner join course c on c.c_id=sc.c_id and c.c_id='02'
 order by sc.s_score desc LIMIT 0,3) b
union all
select c.* from (
 select st.s_id,st.s_name,c.c_id,c.c_name,sc.s_score from student st
 left join score sc on sc.s_id=st.s_id
 inner join course c on c.c_id=sc.c_id and c.c_id='03'
 order by sc.s_score desc LIMIT 0,3) c

-- 26、查詢每門課程被選修的學生數(shù) 
select c.c_id,c.c_name,count(1) from course c 
left join score sc on sc.c_id=c.c_id
inner join student st on st.s_id=c.c_id
group by st.s_id

-- 27、查詢出只有兩門課程的全部學生的學號和姓名
select st.s_id,st.s_name from student st 
left join score sc on sc.s_id=st.s_id
inner join course c on c.c_id=sc.c_id 
group by st.s_id having count(1)=2

-- 28、查詢男生、女生人數(shù)
select st.s_sex,count(1) from student st group by st.s_sex

-- 29、查詢名字中含有"風"字的學生信息
select st.* from student st where st.s_name like "%風%";

-- 30、查詢同名同性學生名單，并統(tǒng)計同名人數(shù) 
select st.*,count(1) from student st group by st.s_name,st.s_sex having count(1)>1

-- 31、查詢1990年出生的學生名單
select st.* from student st where st.s_birth like "1990%";

-- 32、查詢每門課程的平均成績，結果按平均成績降序排列，平均成績相同時，按課程編號升序排列 
select c.c_id,c.c_name,avg(sc.s_score) from course c
inner join score sc on sc.c_id=c.c_id 
group by c.c_id order by avg(sc.s_score) desc,c.c_id asc

-- 33、查詢平均成績大于等于85的所有學生的學號、姓名和平均成績
select st.s_id,st.s_name,avg(sc.s_score) from student st
left join score sc on sc.s_id=st.s_id
group by st.s_id having avg(sc.s_score)>=85

-- 34、查詢課程名稱為"數(shù)學"，且分數(shù)低于60的學生姓名和分數(shù) 
select st.s_id,st.s_name,sc.s_score from student st
inner join score sc on sc.s_id=st.s_id and sc.s_score<60
inner join course c on c.c_id=sc.c_id and c.c_name ="數(shù)學" 

-- 35、查詢所有學生的課程及分數(shù)情況；
select st.s_id,st.s_name,c.c_name,sc.s_score from student st
left join score sc on sc.s_id=st.s_id
left join course c on c.c_id =sc.c_id
order by st.s_id,c.c_name

-- 36、查詢任何一門課程成績在70分以上的姓名、課程名稱和分數(shù)
select st2.s_id,st2.s_name,c2.c_name,sc2.s_score from student st2
left join score sc2 on sc2.s_id=st2.s_id
left join course c2 on c2.c_id=sc2.c_id 
where st2.s_id in(
select st.s_id from student st 
left join score sc on sc.s_id=st.s_id 
group by st.s_id having min(sc.s_score)>=70)
order by s_id

-- 37、查詢不及格的課程
select st.s_id,c.c_name,st.s_name,sc.s_score from student st
inner join score sc on sc.s_id=st.s_id and sc.s_score<60
inner join course c on c.c_id=sc.c_id 

-- 38、查詢課程編號為01且課程成績在80分以上的學生的學號和姓名
select st.s_id,st.s_name,sc.s_score from student st
inner join score sc on sc.s_id=st.s_id and sc.c_id="01" and sc.s_score>=80

-- 39、求每門課程的學生人數(shù)
select c.c_id,c.c_name,count(1) from course c
inner join score sc on sc.c_id=c.c_id
group by c.c_id

-- 40、查詢選修"張三"老師所授課程的學生中，成績最高的學生信息及其成績 
select st.*,c.c_name,sc.s_score,t.t_name from student st
inner join score sc on sc.s_id=st.s_id
inner join course c on c.c_id=sc.c_id 
inner join teacher t on t.t_id=c.t_id and t.t_name="張三"
order by sc.s_score desc
limit 0,1

-- 41、查詢不同課程成績相同的學生的學生編號、課程編號、學生成績 
select st.s_id,st.s_name,sc.c_id,sc.s_score from student st 
left join score sc on sc.s_id=st.s_id
left join course c on c.c_id=sc.c_id
where (
select count(1) from student st2 
left join score sc2 on sc2.s_id=st2.s_id
left join course c2 on c2.c_id=sc2.c_id
where sc.s_score=sc2.s_score and c.c_id!=c2.c_id 
)>1

-- 42、查詢每門功成績最好的前兩名 
select a.* from (select st.s_id,st.s_name,c.c_name,sc.s_score from student st
left join score sc on sc.s_id=st.s_id
inner join course c on c.c_id=sc.c_id and c.c_id="01"
order by sc.s_score desc limit 0,2) a
union all
select b.* from (select st.s_id,st.s_name,c.c_name,sc.s_score from student st
left join score sc on sc.s_id=st.s_id
inner join course c on c.c_id=sc.c_id and c.c_id="02"
order by sc.s_score desc limit 0,2) b
union all
select c.* from (select st.s_id,st.s_name,c.c_name,sc.s_score from student st
left join score sc on sc.s_id=st.s_id
inner join course c on c.c_id=sc.c_id and c.c_id="03"
order by sc.s_score desc limit 0,2) c
 
-- 借鑒(更準確,漂亮):
 select a.s_id,a.c_id,a.s_score from score a
 where (select COUNT(1) from score b where b.c_id=a.c_id and b.s_score>=a.s_score)<=2 order by a.c_id

-- 43、統(tǒng)計每門課程的學生選修人數(shù)（超過5人的課程才統(tǒng)計）。要求輸出課程號和選修人數(shù)，查詢結果按人數(shù)降序排列，
--  若人數(shù)相同，按課程號升序排列 
select sc.c_id,count(1) from score sc
left join course c on c.c_id=sc.c_id
group by c.c_id having count(1)>5
order by count(1) desc,sc.c_id asc

-- 44、檢索至少選修兩門課程的學生學號 
select st.s_id from student st 
left join score sc on sc.s_id=st.s_id
group by st.s_id having count(1)>=2

-- 45、查詢選修了全部課程的學生信息
select st.* from student st 
left join score sc on sc.s_id=st.s_id
group by st.s_id having count(1)=(select count(1) from course)

-- 46、查詢各學生的年齡
 select st.*,timestampdiff(year,st.s_birth,now()) from student st

-- 47、查詢本周過生日的學生
 -- 此處可能有問題,week函數(shù)取的為當前年的第幾周,2017-12-12是第50周而2018-12-12是第49周,可以取月份,day,星期幾(%w),
 -- 再判斷本周是否會持續(xù)到下一個月進行判斷,太麻煩,不會寫
select st.* from student st 
where week(now())=week(date_format(st.s_birth,'%Y%m%d'))

-- 48、查詢下周過生日的學生
select st.* from student st 
where week(now())+1=week(date_format(st.s_birth,'%Y%m%d'))

-- 49、查詢本月過生日的學生
select st.* from student st 
where month(now())=month(date_format(st.s_birth,'%Y%m%d'))

-- 50、查詢下月過生日的學生
 -- 注意:當 當前月為12時,用month(now())+1為13而不是1,可用timestampadd()函數(shù)或mod取模
select st.* from student st 
where month(timestampadd(month,1,now()))=month(date_format(st.s_birth,'%Y%m%d'))
-- 或
select st.* from student st where (month(now()) + 1) mod 12 = month(date_format(st.s_birth,'%Y%m%d'))