-- 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.*,b.s_score as01_score,c.s_score as02_score from student a join score b on a.s_id=b.s_id and b.c_id='01'leftjoin score c on a.s_id=c.s_id and c.c_id='02'or c.c_id =NULLwhere b.s_score>c.s_score
-- 2、查询"01"课程比"02"课程成绩低的学生的信息及课程分数 select a.*,b.s_score as01_score,c.s_score as02_score from student a leftjoin score b on a.s_id=b.s_id and b.c_id='01'or b.c_id=NULLjoin score c on a.s_id=c.s_id and c.c_id='02'where b.s_score<c.s_score
-- 3、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 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_idGROUPBY b.s_id,b.s_name HAVINGROUND(AVG(a.s_score),2)>=60;-- 4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩-- (包括有成绩的和无成绩的) select b.s_id,b.s_name,ROUND(AVG(a.s_score),2)as avg_score from student b leftjoin score a on b.s_id = a.s_idGROUPBY b.s_id,b.s_name HAVINGROUND(AVG(a.s_score),2)<60unionselect a.s_id,a.s_name,0as avg_score from student a where a.s_id notin(selectdistinct s_id from score);-- 5、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select a.s_id,a.s_name,count(b.c_id)as sum_course,sum(b.s_score)as sum_score from student a leftjoin score b on a.s_id=b.s_idGROUPBY a.s_id,a.s_name;-- 6、查询"李"姓老师的数量 selectcount(t_id)from teacher where t_name like'李%';-- 7、查询学过"张三"老师授课的同学的信息 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 ='张三'));-- 8、查询没学过"张三"老师授课的同学的信息 select*from student c where c.s_id notin(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 ='张三')));-- 9、查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息 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';-- 10、查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息select a.*from student a where a.s_id in(select s_id from score where c_id='01')and a.s_id notin(select s_id from score where c_id='02')-- 11、查询没有学全所有课程的同学的信息 select s.*from student s where s.s_id in(select s_id from score where s_id notin(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 select*from student where s_id in(selectdistinct a.s_id from score a where a.c_id in(select a.c_id from score a where a.s_id='01'));-- 13、查询和"01"号的同学学习的课程完全相同的其他同学的信息 select a.*from student a where a.s_id in(selectdistinct s_id from score where s_id!='01'and c_id in(select c_id from score where s_id='01')groupby s_id havingcount(1)=(selectcount(1)from score where s_id='01'));-- 14、查询没学过"张三"老师讲授的任一门课程的学生姓名 select a.s_name from student a where a.s_id notin(select s_id from score where c_id =(select c_id from course where t_id =(select t_id from teacher where t_name ='张三'))groupby s_id);-- 15、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 a.s_id,a.s_name,ROUND(AVG(b.s_score))from student a leftjoin score b on a.s_id = b.s_idwhere a.s_id in(select s_id from score where s_score<60GROUPBY s_id havingcount(1)>=2)GROUPBY a.s_id,a.s_name
-- 16、检索"01"课程分数小于60,按分数降序排列的学生信息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<60ORDERBY b.s_score DESC;-- 17、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 a.s_id,(select s_score from score where s_id=a.s_id and c_id='01')as 语文,(select s_score from score where s_id=a.s_id and c_id='02')as 数学,(select s_score from score where s_id=a.s_id and c_id='03')as 英语,round(avg(s_score),2)as 平均分 from score a GROUPBY a.s_id ORDERBY 平均分 DESC;-- 18.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:>=90select a.c_id,b.c_name,MAX(s_score),MIN(s_score),ROUND(AVG(s_score),2),ROUND(100*(SUM(casewhen a.s_score>=60then1else0end)/SUM(casewhen a.s_score then1else0end)),2)as 及格率,ROUND(100*(SUM(casewhen a.s_score>=70and a.s_score<=80then1else0end)/SUM(casewhen a.s_score then1else0end)),2)as 中等率,ROUND(100*(SUM(casewhen a.s_score>=80and a.s_score<=90then1else0end)/SUM(casewhen a.s_score then1else0end)),2)as 优良率,ROUND(100*(SUM(casewhen a.s_score>=90then1else0end)/SUM(casewhen a.s_score then1else0end)),2)as 优秀率from score a leftjoin course b on a.c_id = b.c_id GROUPBY a.c_id,b.c_name
-- 19、按各科成绩进行排序,并显示排名(实现不完全)-- mysql没有rank函数select a.s_id,a.c_id,@i:=@i+1as i保留排名,@k:=(casewhen@score=a.s_score then@kelse@iend)as rank不保留排名,@score:=a.s_score as scorefrom(select s_id,c_id,s_score from score WHERE c_id='01'GROUPBY s_id,c_id,s_score ORDERBY s_score DESC)a,(select@k:=0,@i:=0,@score:=0)sunionselect a.s_id,a.c_id,@i:=@i+1as i,@k:=(casewhen@score=a.s_score then@kelse@iend)as rank,@score:=a.s_score as scorefrom(select s_id,c_id,s_score from score WHERE c_id='02'GROUPBY s_id,c_id,s_score ORDERBY s_score DESC)a,(select@k:=0,@i:=0,@score:=0)sunionselect a.s_id,a.c_id,@i:=@i+1as i,@k:=(casewhen@score=a.s_score then@kelse@iend)as rank,@score:=a.s_score as scorefrom(select s_id,c_id,s_score from score WHERE c_id='03'GROUPBY s_id,c_id,s_score ORDERBY s_score DESC)a,(select@k:=0,@i:=0,@score:=0)s
-- 20、查询学生的总成绩并进行排名select a.s_id,@i:=@i+1as i,@k:=(casewhen@score=a.sum_score then@kelse@iend)as rank,@score:=a.sum_score as score
from(select s_id,SUM(s_score)as sum_score from score GROUPBY s_id ORDERBY sum_score DESC)a,(select@k:=0,@i:=0,@score:=0)s
-- 21、查询不同老师所教不同课程平均分从高到低显示 select a.t_id,c.t_name,a.c_id,ROUND(avg(s_score),2)as avg_score from course aleftjoin score b on a.c_id=b.c_id leftjoin teacher c on a.t_id=c.t_idGROUPBY a.c_id,a.t_id,c.t_name ORDERBY avg_score DESC;-- 22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩 select d.*,c.排名,c.s_score,c.c_id from(select a.s_id,a.s_score,a.c_id,@i:=@i+1as 排名 from score a,(select@i:=0)s where a.c_id='01')cleftjoin student d on c.s_id=d.s_idwhere 排名 BETWEEN2AND3UNIONselect d.*,c.排名,c.s_score,c.c_id from(select a.s_id,a.s_score,a.c_id,@j:=@j+1as 排名 from score a,(select@j:=0)s where a.c_id='02')cleftjoin student d on c.s_id=d.s_idwhere 排名 BETWEEN2AND3UNIONselect d.*,c.排名,c.s_score,c.c_id from(select a.s_id,a.s_score,a.c_id,@k:=@k+1as 排名 from score a,(select@k:=0)s where a.c_id='03')cleftjoin student d on c.s_id=d.s_idwhere 排名 BETWEEN2AND3;-- 23、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],[0-60]及所占百分比selectdistinct 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 aleftjoin(select c_id,SUM(casewhen s_score >85and s_score <=100then1else0end)as`85-100`,ROUND(100*(SUM(casewhen s_score >85and s_score <=100then1else0end)/count(*)),2)as 百分比from score GROUPBY c_id)b on a.c_id=b.c_idleftjoin(select c_id,SUM(casewhen s_score >70and s_score <=85then1else0end)as`70-85`,ROUND(100*(SUM(casewhen s_score >70and s_score <=85then1else0end)/count(*)),2)as 百分比from score GROUPBY c_id)c on a.c_id=c.c_idleftjoin(select c_id,SUM(casewhen s_score >60and s_score <=70then1else0end)as`60-70`,ROUND(100*(SUM(casewhen s_score >60and s_score <=70then1else0end)/count(*)),2)as 百分比from score GROUPBY c_id)d on a.c_id=d.c_idleftjoin(select c_id,SUM(casewhen s_score >=0and s_score <=60then1else0end)as`0-60`,ROUND(100*(SUM(casewhen s_score >=0and s_score <=60then1else0end)/count(*)),2)as 百分比from score GROUPBY c_id)e on a.c_id=e.c_idleftjoin course f on a.c_id = f.c_id
-- 24、查询学生平均成绩及其名次 select a.s_id,@i:=@i+1as'不保留空缺排名',@k:=(casewhen@avg_score=a.avg_s then@kelse@iend)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 GROUPBY s_id)a,(select@avg_score:=0,@i:=0,@k:=0)b;-- 25、查询各科成绩前三名的记录-- 1.选出b表比a表成绩大的所有组-- 2.选出比当前id成绩大的 小于三个的select a.s_id,a.c_id,a.s_score from score a leftjoin score b on a.c_id = b.c_id and a.s_score<b.s_scoregroupby a.s_id,a.c_id,a.s_score HAVINGCOUNT(b.s_id)<3ORDERBY a.c_id,a.s_score DESC-- 26、查询每门课程被选修的学生数 select c_id,count(s_id)from score a GROUPBY c_id
-- 27、查询出只有两门课程的全部学生的学号和姓名 select s_id,s_name from student where s_id in(select s_id from score GROUPBY s_id HAVINGCOUNT(c_id)=2);-- 28、查询男生、女生人数 select s_sex,COUNT(s_sex)as 人数 from student GROUPBY s_sex
-- 29、查询名字中含有"风"字的学生信息select*from student where s_name like'%风%';-- 30、查询同名同性学生名单,并统计同名人数 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_sexGROUPBY a.s_name,a.s_sex
-- 31、查询1990年出生的学生名单 select s_name from student where s_birth like'1990%'-- 32、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 c_id,ROUND(AVG(s_score),2)as avg_score from score GROUPBY c_id ORDERBY avg_score DESC,c_id ASC-- 33、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 select a.s_id,b.s_name,ROUND(avg(a.s_score),2)as avg_score from score aleftjoin student b on a.s_id=b.s_id GROUPBY s_id HAVING avg_score>=85-- 34、查询课程名称为"数学",且分数低于60的学生姓名和分数 select a.s_name,b.s_score from score b LEFTJOIN student a on a.s_id=b.s_id where b.c_id=(select c_id from course where c_name ='数学')and b.s_score<60-- 35、查询所有学生的课程及分数情况; select a.s_id,a.s_name,SUM(case c.c_name when'语文'then b.s_score else0end)as'语文',SUM(case c.c_name when'数学'then b.s_score else0end)as'数学',SUM(case c.c_name when'英语'then b.s_score else0end)as'英语',SUM(b.s_score)as'总分'from student a leftjoin score b on a.s_id = b.s_id leftjoin course c on b.c_id = c.c_id GROUPBY a.s_id,a.s_name -- 36、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 a.s_name,b.c_name,c.s_score from course b leftjoin score c on b.c_id = c.c_idleftjoin student a on a.s_id=c.s_id where c.s_score>=70-- 37、查询不及格的课程select a.s_id,a.c_id,b.c_name,a.s_score from score a leftjoin course b on a.c_id = b.c_idwhere a.s_score<60--38、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.s_id,b.s_name from score a LEFTJOIN student b on a.s_id = b.s_idwhere a.c_id ='01'and a.s_score>80-- 39、求每门课程的学生人数 selectcount(*)from score GROUPBY c_id;-- 40、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-- 查询老师id select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='张三'-- 查询最高分(可能有相同分数)selectMAX(s_score)from score where c_id='02'-- 查询信息select a.*,b.s_score,b.c_id,c.c_name from student aLEFTJOIN score b on a.s_id = b.s_idLEFTJOIN course c on b.c_id=c.c_idwhere b.c_id =(select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='张三')and b.s_score in(selectMAX(s_score)from score where c_id='02')-- 41、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 selectDISTINCT 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、查询每门功成绩最好的前两名 -- 牛逼的写法select a.s_id,a.c_id,a.s_score from score awhere(selectCOUNT(1)from score b where b.c_id=a.c_id and b.s_score>=a.s_score)<=2ORDERBY a.c_id
-- 43、统计每门课程的学生选修人数(超过5人的课程才统计)。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 c_id,count(*)as total from score GROUPBY c_id HAVING total>5ORDERBY total,c_id ASC-- 44、检索至少选修两门课程的学生学号 select s_id,count(*)as sel from score GROUPBY s_id HAVING sel>=2-- 45、查询选修了全部课程的学生信息 select*from student where s_id in(select s_id from score GROUPBY s_id HAVINGcount(*)=(selectcount(*)from course))--46、查询各学生的年龄-- 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 s_birth,(DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(s_birth,'%Y')-(casewhen DATE_FORMAT(NOW(),'%m%d')>DATE_FORMAT(s_birth,'%m%d')then0else1end))as agefrom student;-- 47、查询本周过生日的学生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、查询下周过生日的学生select*from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1=WEEK(s_birth)-- 49、查询本月过生日的学生select*from student whereMONTH(DATE_FORMAT(NOW(),'%Y%m%d'))=MONTH(s_birth)-- 50、查询下月过生日的学生select*from student whereMONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1=MONTH(s_birth)
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