經典sql題練習50題

-- 一、查詢"01"課程比"02"課程成績高的學生的信息及課程分數	
	
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
	
--也能夠這樣寫
	select a.*,b.s_score as 01_score,c.s_score as 02_score 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' 
			and b.s_score>c.s_score
-- 二、查詢"01"課程比"02"課程成績低的學生的信息及課程分數
	
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
			

-- 三、查詢平均成績大於等於60分的同窗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 avg_score >=60;
	

-- 四、查詢平均成績小於60分的同窗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 avg_score <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);


-- 五、查詢全部同窗的學生編號、學生姓名、選課總數、全部課程的總成績
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;
			
			
-- 六、查詢"李"姓老師的數量 
select count(t_id) from teacher where t_name like '李%';
	
-- 七、查詢學過"張三"老師授課的同窗的信息 
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'));

-- 八、查詢沒學過"張三"老師授課的同窗的信息 
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 a.c_id from course a join teacher b on a.t_id = b.t_id where t_name ='張三'));
-- 九、查詢學過編號爲"01"而且也學過編號爲"02"的課程的同窗的信息

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';
	
-- 十、查詢學過編號爲"01"可是沒有學過編號爲"02"的課程的同窗的信息
			
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')
			

-- 十一、查詢沒有學全全部課程的同窗的信息 
--@wendiepei的寫法
select s.* from student s 
left join Score s1 on s1.s_id=s.s_id
group by s.s_id having count(s1.c_id)<(select count(*) from course)	
--@k1051785839的寫法
select *
from student
where s_id not in(
select s_id from score t1  
group by s_id having count(*) =(select count(distinct c_id)  from course)) 
-- 十二、查詢至少有一門課與學號爲"01"的同窗所學相同的同窗的信息 

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')
	);
			
-- 1三、查詢和"01"號的同窗學習的課程徹底相同的其餘同窗的信息 
--@ouyang_1993的寫法
SELECT
 Student.*
FROM
 Student
WHERE
 s_id IN (SELECT s_id FROM Score GROUP BY s_id HAVING COUNT(s_id) = (
    #下面的語句是找到'01'同窗學習的課程數
    SELECT COUNT(c_id) FROM Score WHERE s_id = '01'
   )
 )
AND s_id NOT IN (
 #下面的語句是找到學過‘01’同窗沒學過的課程，有哪些同窗。並排除他們
 SELECT s_id FROM Score
 WHERE c_id IN(
   #下面的語句是找到‘01’同窗沒學過的課程
   SELECT DISTINCT c_id FROM Score
   WHERE c_id NOT IN (
     #下面的語句是找出‘01’同窗學習的課程
     SELECT c_id FROM Score WHERE s_id = '01'
    )
  ) GROUP BY s_id
) #下面的條件是排除01同窗
AND s_id NOT IN ('01')
--@k1051785839的寫法
SELECT
 t3.*
FROM
 (
  SELECT
   s_id,
   group_concat(c_id ORDER BY c_id) group1
  FROM
   score
  WHERE
   s_id <> '01'
  GROUP BY
   s_id
 ) t1
INNER JOIN (
 SELECT
  group_concat(c_id ORDER BY c_id) group2
 FROM
  score
 WHERE
  s_id = '01'
 GROUP BY
  s_id
) t2 ON t1.group1 = t2.group2
INNER JOIN student t3 ON t1.s_id = t3.s_id

-- 1四、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')));

-- 1五、查詢兩門及其以上不及格課程的同窗的學號，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

-- 1六、檢索"01"課程分數小於60，按分數降序排列的學生信息
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;
		
-- 1七、按平均成績從高到低顯示全部學生的全部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;
--@喝完這杯還有一箱的寫法
SELECT a.s_id,MAX(CASE a.c_id WHEN '01' THEN a.s_score END ) 語文, 
MAX(CASE a.c_id WHEN '02' THEN a.s_score END ) 數學, 
MAX(CASE a.c_id WHEN '03' THEN a.s_score END ) 英語, 
avg(a.s_score),b.s_name FROM Score a JOIN Student b ON a.s_id=b.s_id GROUP BY a.s_id ORDER BY 5 DESC		
-- 18.查詢各科成績最高分、最低分和平均分：以以下形式顯示：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
--及格爲>=60，中等爲：70-80，優良爲：80-90，優秀爲：>=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
	
-- 1九、按各科成績進行排序，並顯示排名
-- mysql沒有rank函數
	select a.s_id,a.c_id,
        @i:=@i +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 GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s
--@k1051785839的寫法
(select * from (select 
t1.c_id,
t1.s_score,
(select count(distinct t2.s_score) from score t2 where t2.s_score>=t1.s_score and t2.c_id='01') rank
FROM score t1 where t1.c_id='01'
order by t1.s_score desc) t1)
union
(select * from (select 
t1.c_id,
t1.s_score,
(select count(distinct t2.s_score) from score t2 where t2.s_score>=t1.s_score and t2.c_id='02') rank
FROM score t1 where t1.c_id='02'
order by t1.s_score desc) t2)
union
(select * from (select 
t1.c_id,
t1.s_score,
(select count(distinct t2.s_score) from score t2 where t2.s_score>=t1.s_score and t2.c_id='03') rank
FROM score t1 where t1.c_id='03'
order by t1.s_score desc) t3)
-- 20、查詢學生的總成績並進行排名
select a.s_id,
	@i:=@i+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
	
-- 2一、查詢不一樣老師所教不一樣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;
-- 2二、查詢全部課程的成績第2名到第3名的學生信息及該課程成績
			
			select d.*,c.排名,c.s_score,c.c_id from (
                select a.s_id,a.s_score,a.c_id,@i:=@i+1 as 排名 from score a,(select @i:=0)s where a.c_id='01'  
								ORDER BY a.s_score DESC  
            )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:=@j+1 as 排名 from score a,(select @j:=0)s where a.c_id='02'  
								ORDER BY a.s_score DESC
            )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:=@k+1 as 排名 from score a,(select @k:=0)s where a.c_id='03' 
								ORDER BY a.s_score DESC
            )c
            left join student d on c.s_id=d.s_id
            where 排名 BETWEEN 2 AND 3;
			
-- 2三、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
				 
-- 2四、查詢學平生均成績及其名次 

		select a.s_id,
				@i:=@i+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 ORDER BY avg_s DESC)a,(select @avg_score:=0,@i:=0,@k:=0)b;
-- 2五、查詢各科成績前三名的記錄
			-- 1.選出b表比a表成績大的全部組
			-- 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

-- 2六、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

-- 2七、查詢出只有兩門課程的所有學生的學號和姓名 
		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);

-- 2八、查詢男生、女生人數 
		select s_sex,COUNT(s_sex) as 人數  from student GROUP BY s_sex

-- 2九、查詢名字中含有"風"字的學生信息

		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



-- 3一、查詢1990年出生的學生名單
		
		select s_name from student where s_birth like '1990%'

-- 3二、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

-- 3三、查詢平均成績大於等於85的全部學生的學號、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
	
-- 3四、查詢課程名稱爲"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 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

-- 3五、查詢全部學生的課程及分數狀況； 
	
		
		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


 -- 3六、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

		

-- 3七、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 
		
--3八、查詢課程編號爲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

-- 3九、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，成績最高的學生信息及其成績

		
		-- 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'
		-- 查詢信息
		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')


-- 4一、查詢不一樣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
	

-- 4二、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


-- 4三、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
		
-- 4四、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

-- 4五、查詢選修了所有課程的學生信息 
		select * from student where s_id in(		
			select s_id from score GROUP BY s_id HAVING count(*)=(select count(*) from course))


--4六、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;


-- 4七、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'))

-- 4八、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)

-- 4九、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)

　　

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