总结一些面试时常考的sql语句

数据准备

--创建测试数据
create table student(s varchar(10),sname nvarchar(10),sage datetime,ssex nvarchar(10));
insert into student values('01','赵英','1990-01-01','男');
insert into student values('02','钱雄','1990-12-21','男');
insert into student values('03','孙豪','1990-05-20','男');
insert into student values('04','李杰','1990-08-06','男');
insert into student values('05','周梅','1991-12-01','女');
insert into student values('06','吴兰','1992-03-01','女');
insert into student values('07','郑竹','1989-07-01','女');
insert into student values('08','王菊','1990-01-20','女');
create table course(c varchar(10),cname nvarchar(10),t varchar(10));
insert into course values('01','语文','02');
insert into course values('02','数学','01');
insert into course values('03','英语','03');
insert into course values('04','物理','01');
create table teacher(t varchar(10),tname nvarchar(10));
insert into teacher values('01','张三');
insert into teacher values('02','李四');
insert into teacher values('03','王五');
create table sc(s varchar(10),c varchar(10),score decimal(18,1));
insert into sc values('01','01',80);
insert into sc values('01','02',90);
insert into sc values('01','03',99);
insert into sc values('02','01',70);
insert into sc values('02','02',60);
insert into sc values('02','03',80);
insert into sc values('03','01',80);
insert into sc values('03','02',80);
insert into sc values('03','03',80);
insert into sc values('04','01',50);
insert into sc values('04','02' 30);
insert into sc values('04','03',20);
insert into sc values('05','01',76);
insert into sc values('05','02',87);
insert into sc values('06','01',31);
insert into sc values('06','03',34);
insert into sc values('07','02',89);
insert into sc values('07','03',98);

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--1、查询"01"课程比"02"课程成绩高的学生的信息及课程分数
自己一开始想的：
select * from (select m.s, m.score "01",n.score "02" from (select s,score from sc where sc.c="01") m, (select s,score from sc where sc.c="02")n where m.s=n.s and m.score>n.score) o , student where o.s=student.s;


select * from student s ,sc s1,sc s2 where s.s = s1.s and s1.c='01' and s.s = s2.s and s2.c='02' and s1.score>s2.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 s.s,s.sname,avg(sc.score) avgscore from student s,sc where s.s = sc.s group by sc.s having avg(sc.score)>=60;

--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 s.s,s.sname,count(sc.c) ctotal,ifnull(sum(sc.score),0) stotal from student s left join sc on s.s = sc.s group by s.s;

--6、查询"李"姓老师的数量 
select count(*) from teacher t where t.tname like '李%';

--7、查询学过"张三"老师授课的同学的信息 
select s.s,s.sname,s.sage,s.ssex from teacher t ,course c ,sc,student s where t.tname="张三" and t.t=c.t and c.c=sc.c and sc.s = s.s; 
--8、查询没学过"张三"老师授课的同学的信息 
select * from student s where s.s not in (select s.s from teacher t ,course c ,sc,student s where t.tname="张三" and t.t=c.t and c.c=sc.c and sc.s = s.s);

--11、查询没有学全所有课程的同学的信息 
select s.s,s.sname,s.sage,s.ssex from student s,sc,(select count(sc.c) m from sc) n, (select count(*) m from course) c where c.m !=n.m and sc.s=s.s group by s.s;

--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 * from student s,(select sc.s,avg(sc.score) from sc where sc.score<60 group by sc.s having (count(*)>=2)) m where s.s=m.s;

--16、检索"01"课程分数小于60，按分数降序排列的学生信息
select * from  student s right join (select * from sc where sc.c='01' and sc.score<60) m on m.s=s.s ;

--26、查询每门课程被选修的学生数 
 select c.c,count(sc.s) from course c left join sc on c.c=sc.c group by c.c;

--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.c, ifnull(avg(sc.score),0) from course c left join sc on c.c=sc.c group by c.c order by avg(sc.score) desc;

--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
select s.*,c.cname,max(sc.score) from student s,sc,course c ,teacher t where s.s=sc.s and c.c=sc.c and c.t=t.t and t.tname="张三";