--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`) ); --插入學生表測試資料 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' , '李雲' , '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'); --課程表測試資料 insert into Course values('01' , '語文' , '02'); insert into Course values('02' , '數學' , '01'); insert into Course values('03' , '英語' , '03');

--教師表測試資料 insert into Teacher values('01' , '張三'); insert into Teacher values('02' , '李四'); insert into Teacher values('03' , '王五');

--成績表測試資料 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);  

-- 1、查詢"01"課程比"02"課程成績高的學生的資訊及課程分數  

select a.* ,b.s_score as 01_score,c.s_score as 02_score from      student a      join score b on a.s_id=b.s_id and b.c_id='01'     left join score c on a.s_id=c.s_id and c.c_id='02' or c.c_id = NULL where b.s_score>c.s_score

-- 2、查詢"01"課程比"02"課程成績低的學生的資訊及課程分數

select a.* ,b.s_score as 01_score,c.s_score as 02_score from      student a left join score b on a.s_id=b.s_id and b.c_id='01' or b.c_id=NULL       join score c on a.s_id=c.s_id and c.c_id='02' where b.s_score<c.s_score

-- 3、查詢平均成績大於等於60分的同學的學生編號和學生姓名和平均成績 select b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from      student b      join score a on b.s_id = a.s_id     GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)>=60;

-- 4、查詢平均成績小於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 b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from      student b      left join score a on b.s_id = a.s_id     GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)<60     union select a.s_id,a.s_name,0 as avg_score from      student a      where a.s_id not in (                 select distinct s_id from score);

-- 5、查詢所有同學的學生編號、學生姓名、選課總數、所有課程的總成績 select a.s_id,a.s_name,count(b.c_id) as sum_course,sum(b.s_score) as sum_score from      student a      left join score b on a.s_id=b.s_id     GROUP BY a.s_id,a.s_name;

-- 6、查詢"李"姓老師的數量  select count(t_id) from teacher where t_name like '李%';

-- 7、查詢學過"張三"老師授課的同學的資訊  select a.* from      student a      join score b on a.s_id=b.s_id where b.c_id in(         select c_id from course where t_id =(             select t_id from teacher where t_name = '張三'));

-- 8、查詢沒學過"張三"老師授課的同學的資訊  select * from      student c      where c.s_id not in(         select a.s_id from student a join score b on a.s_id=b.s_id where b.c_id in(             select c_id from course where t_id =(                 select t_id from teacher where t_name = '張三'))); -- 9、查詢學過編號為"01"並且也學過編號為"02"的課程的同學的資訊

select a.* from      student a,score b,score c      where a.s_id = b.s_id  and a.s_id = c.s_id and b.c_id='01' and c.c_id='02';

-- 10、查詢學過編號為"01"但是沒有學過編號為"02"的課程的同學的資訊

select a.* from      student a      where a.s_id in (select s_id from score where c_id='01' ) and a.s_id not in(select s_id from score where c_id='02')

-- 11、查詢沒有學全所有課程的同學的資訊 

select s.* from      student s where s.s_id in(         select s_id from score where s_id not in(             select a.s_id from score a                  join score b on a.s_id = b.s_id and b.c_id='02'                 join score c on a.s_id = c.s_id and c.c_id='03'             where a.c_id='01'))

-- 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資訊 

select * from student where s_id in(     select distinct a.s_id from score a where a.c_id in(select a.c_id from score a where a.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資訊 

select a.* from student a where a.s_id in(     select distinct s_id from score where s_id!='01' and c_id in(select c_id from score where s_id='01')     group by s_id      having count(1)=(select count(1) from score where 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 a.s_name from student a where a.s_id not in (     select s_id from score where c_id =                  (select c_id from course where t_id =(                     select t_id from teacher where t_name = '張三'))                  group by s_id);

-- 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 a.s_id,a.s_name,ROUND(AVG(b.s_score)) from      student a      left join score b on a.s_id = b.s_id     where a.s_id in(             select s_id from score where s_score<60 GROUP BY  s_id having count(1)>=2)     GROUP BY a.s_id,a.s_name

-- 16、檢索"01"課程分數小於60，按分數降序排列的學生資訊 select a.*,b.c_id,b.s_score from      student a,score b      where a.s_id = b.s_id and b.c_id='01' and b.s_score<60 ORDER BY b.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 select a.s_id,(select s_score from score where s_id=a.s_id and c_id='01') as 語文,                 (select s_score from score where s_id=a.s_id and c_id='02') as 數學,                 (select s_score from score where s_id=a.s_id and c_id='03') as 英語,             round(avg(s_score),2) as 平均分 from score a  GROUP BY a.s_id ORDER BY 平均分 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，優良率，優秀率 --及格為>=60，中等為：70-80，優良為：80-90，優秀為：>=90 select a.c_id,b.c_name,MAX(s_score),MIN(s_score),ROUND(AVG(s_score),2),     ROUND(100*(SUM(case when a.s_score>=60 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 及格率,     ROUND(100*(SUM(case when a.s_score>=70 and a.s_score<=80 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 中等率,     ROUND(100*(SUM(case when a.s_score>=80 and a.s_score<=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 優良率,     ROUND(100*(SUM(case when a.s_score>=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 優秀率     from score a left join course b on a.c_id = b.c_id GROUP BY a.c_id,b.c_name

-- 19、按各科成績進行排序，並顯示排名(實現不完全) -- mysql沒有rank函式     select a.s_id,a.c_id,         @i:[email protected] +1 as i保留排名,         @k:=(case when @score=a.s_score then @k else @i end) as rank不保留排名,         @score:=a.s_score as score     from (         select s_id,c_id,s_score from score WHERE c_id='01' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC )a,(select @k:=0,@i:=0,@score:=0)s     union     select a.s_id,a.c_id,         @i:[email protected] +1 as i,         @k:=(case when @score=a.s_score then @k else @i end) as rank,         @score:=a.s_score as score     from (         select s_id,c_id,s_score from score WHERE c_id='02' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC )a,(select @k:=0,@i:=0,@score:=0)s     union     select a.s_id,a.c_id,         @i:[email protected] +1 as i,         @k:=(case when @score=a.s_score then @k else @i end) as rank,         @score:=a.s_score as score     from (         select s_id,c_id,s_score from score WHERE c_id='03' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC )a,(select @k:=0,@i:=0,@score:=0)s

-- 20、查詢學生的總成績並進行排名 select a.s_id,     @i:[email protected]+1 as i,     @k:=(case when @score=a.sum_score then @k else @i end) as rank,     @score:=a.sum_score as score from (select s_id,SUM(s_score) as sum_score from score GROUP BY s_id ORDER BY sum_score DESC)a,     (select @k:=0,@i:=0,@score:=0)s

-- 21、查詢不同老師所教不同課程平均分從高到低顯示 

    select a.t_id,c.t_name,a.c_id,ROUND(avg(s_score),2) as avg_score from course a         left join score b on a.c_id=b.c_id          left join teacher c on a.t_id=c.t_id         GROUP BY a.c_id,a.t_id,c.t_name ORDER BY avg_score DESC; -- 22、查詢所有課程的成績第2名到第3名的學生資訊及該課程成績

            select d.*,c.排名,c.s_score,c.c_id from (                 select a.s_id,a.s_score,a.c_id,@i:[email protected]+1 as 排名 from score a,(select @i:=0)s where a.c_id='01'                 )c             left join student d on c.s_id=d.s_id             where 排名 BETWEEN 2 AND 3             UNION             select d.*,c.排名,c.s_score,c.c_id from (                 select a.s_id,a.s_score,a.c_id,@j:[email protected]+1 as 排名 from score a,(select @j:=0)s where a.c_id='02'                 )c             left join student d on c.s_id=d.s_id             where 排名 BETWEEN 2 AND 3             UNION             select d.*,c.排名,c.s_score,c.c_id from (                 select a.s_id,a.s_score,a.c_id,@k:[email protected]+1 as 排名 from score a,(select @k:=0)s where a.c_id='03'                 )c             left join student d on c.s_id=d.s_id             where 排名 BETWEEN 2 AND 3;

-- 23、統計各科成績各分數段人數：課程編號,課程名稱,[100-85],[85-70],[70-60],[0-60]及所佔百分比

        select distinct f.c_name,a.c_id,b.`85-100`,b.百分比,c.`70-85`,c.百分比,d.`60-70`,d.百分比,e.`0-60`,e.百分比 from score a                 left join (select c_id,SUM(case when s_score >85 and s_score <=100 then 1 else 0 end) as `85-100`,                                             ROUND(100*(SUM(case when s_score >85 and s_score <=100 then 1 else 0 end)/count(*)),2) as 百分比                                 from score GROUP BY c_id)b on a.c_id=b.c_id                 left join (select c_id,SUM(case when s_score >70 and s_score <=85 then 1 else 0 end) as `70-85`,                                             ROUND(100*(SUM(case when s_score >70 and s_score <=85 then 1 else 0 end)/count(*)),2) as 百分比                                 from score GROUP BY c_id)c on a.c_id=c.c_id                 left join (select c_id,SUM(case when s_score >60 and s_score <=70 then 1 else 0 end) as `60-70`,                                             ROUND(100*(SUM(case when s_score >60 and s_score <=70 then 1 else 0 end)/count(*)),2) as 百分比                                 from score GROUP BY c_id)d on a.c_id=d.c_id                 left join (select c_id,SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end) as `0-60`,                                             ROUND(100*(SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end)/count(*)),2) as 百分比                                 from score GROUP BY c_id)e on a.c_id=e.c_id                 left join course f on a.c_id = f.c_id

-- 24、查詢學生平均成績及其名次 

        select a.s_id,                 @i:[email protected]+1 as '不保留空缺排名',                 @k:=(case when @avg_score=a.avg_s then @k else @i end) as '保留空缺排名',                 @avg_score:=avg_s as '平均分'         from (select s_id,ROUND(AVG(s_score),2) as avg_s from score GROUP BY s_id)a,(select @avg_score:=0,@i:=0,@k:=0)b; -- 25、查詢各科成績前三名的記錄             -- 1.選出b表比a表成績大的所有組             -- 2.選出比當前id成績大的 小於三個的         select a.s_id,a.c_id,a.s_score from score a              left join score b on a.c_id = b.c_id and a.s_score<b.s_score             group by a.s_id,a.c_id,a.s_score HAVING COUNT(b.s_id)<3             ORDER BY a.c_id,a.s_score DESC

-- 26、查詢每門課程被選修的學生數 

        select c_id,count(s_id) from score a GROUP BY c_id

-- 27、查詢出只有兩門課程的全部學生的學號和姓名          select s_id,s_name from student where s_id in(                 select s_id from score GROUP BY s_id HAVING COUNT(c_id)=2);

-- 28、查詢男生、女生人數          select s_sex,COUNT(s_sex) as 人數  from student GROUP BY s_sex

-- 29、查詢名字中含有"風"字的學生資訊

        select * from student where s_name like '%風%';

-- 30、查詢同名同性學生名單，並統計同名人數 

        select a.s_name,a.s_sex,count(*) from student a  JOIN                      student b on a.s_id !=b.s_id and a.s_name = b.s_name and a.s_sex = b.s_sex         GROUP BY a.s_name,a.s_sex

-- 31、查詢1990年出生的學生名單

        select s_name from student where 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_id,ROUND(AVG(s_score),2) as avg_score from score GROUP BY c_id ORDER BY avg_score DESC,c_id ASC

-- 33、查詢平均成績大於等於85的所有學生的學號、姓名和平均成績 

    select a.s_id,b.s_name,ROUND(avg(a.s_score),2) as avg_score from score a         left join student b on a.s_id=b.s_id GROUP BY s_id HAVING avg_score>=85

-- 34、查詢課程名稱為"數學"，且分數低於60的學生姓名和分數 

        select a.s_name,b.s_score from score b LEFT JOIN student a on a.s_id=b.s_id where b.c_id=(                     select c_id from course where c_name ='數學') and b.s_score<60

-- 35、查詢所有學生的課程及分數情況； 

        select a.s_id,a.s_name,                     SUM(case c.c_name when '語文' then b.s_score else 0 end) as '語文',                     SUM(case c.c_name when '數學' then b.s_score else 0 end) as '數學',                     SUM(case c.c_name when '英語' then b.s_score else 0 end) as '英語',                     SUM(b.s_score) as  '總分'         from student a left join score b on a.s_id = b.s_id          left join course c on b.c_id = c.c_id          GROUP BY a.s_id,a.s_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；              select a.s_name,b.c_name,c.s_score from course b left join score c on b.c_id = c.c_id                 left join student a on a.s_id=c.s_id where c.s_score>=70

-- 37、查詢不及格的課程         select a.s_id,a.c_id,b.c_name,a.s_score from score a left join course b on a.c_id = b.c_id             where a.s_score<60 

--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 a.s_id,b.s_name from score a LEFT JOIN student b on a.s_id = b.s_id             where a.c_id = '01' and a.s_score>80

-- 39、求每門課程的學生人數          select count(*) from score GROUP BY c_id;

-- 40、查詢選修"張三"老師所授課程的學生中，成績最高的學生資訊及其成績

        -- 查詢老師id            select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='張三'         -- 查詢最高分（可能有相同分數）         select MAX(s_score) from score where c_id='02'         -- 查詢資訊         select a.*,b.s_score,b.c_id,c.c_name from student a             LEFT JOIN score b on a.s_id = b.s_id             LEFT JOIN course c on b.c_id=c.c_id             where b.c_id =(select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='張三')             and b.s_score in (select MAX(s_score) from score where c_id='02')

-- 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 DISTINCT b.s_id,b.c_id,b.s_score from score a,score b where a.c_id != b.c_id and a.s_score = b.s_score

-- 42、查詢每門功成績最好的前兩名          -- 牛逼的寫法     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、統計每門課程的學生選修人數（超過5人的課程才統計）。要求輸出課程號和選修人數，查詢結果按人數降序排列，若人數相同，按課程號升序排列           select c_id,count(*) as total from score GROUP BY c_id HAVING total>5 ORDER BY total,c_id ASC

-- 44、檢索至少選修兩門課程的學生學號          select s_id,count(*) as sel from score GROUP BY s_id HAVING sel>=2

-- 45、查詢選修了全部課程的學生資訊          select * from student where s_id in(                     select s_id from score GROUP BY s_id HAVING count(*)=(select count(*) from course))

--46、查詢各學生的年齡     -- 按照出生日期來算，當前月日 < 出生年月的月日則，年齡減一

    select s_birth,(DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(s_birth,'%Y') -                  (case when DATE_FORMAT(NOW(),'%m%d')>DATE_FORMAT(s_birth,'%m%d') then 0 else 1 end)) as age         from student;

-- 47、查詢本週過生日的學生     select * from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(s_birth)     select * from student where YEARWEEK(s_birth)=YEARWEEK(DATE_FORMAT(NOW(),'%Y%m%d'))

    select WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))

-- 48、查詢下週過生日的學生     select * from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =WEEK(s_birth)

-- 49、查詢本月過生日的學生

    select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d')) =MONTH(s_birth)

-- 50、查詢下月過生日的學生     select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =MONTH(s_birth)