sqlserver sql interview 20 questions [version]

 This article entitled switched nicknamed 'Venus guidance' of the blog - https://blog.csdn.net/fashion2014/article/details/78826299
here part of the topic was not the same wording, and individual topics may achieve even more complete, welcome to correct the error, thank you!

Table names and field

--建表
--学生表
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)
);
--课程表
CREATE TABLE Course(
    c_id  VARCHAR(20),
    c_name VARCHAR(20) NOT NULL DEFAULT '',
    t_id VARCHAR(20) NOT NULL,
    PRIMARY KEY(c_id)
);
--教师表
CREATE TABLE Teacher(
    t_id VARCHAR(20),
    t_name VARCHAR(20) NOT NULL DEFAULT '',
    PRIMARY KEY(t_id)
);
--成绩表
CREATE TABLE Score(
    s_id VARCHAR(20),
    c_id  VARCHAR(20),
    s_score INT,
    PRIMARY KEY(s_id,c_id)
);
--插入学生表测试数据
insert into Student values('01' , '赵雷' , '1990-01-01' , '男');
insert into Student values('02' , '钱电' , '1990-12-21' , '男');
insert into Student values('03' , '孙风' , '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' , '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');
--课程表测试数据
insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');

--教师表测试数据
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');

--成绩表测试数据
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);

Sql statement and exercises

-- 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 st.*,sc1.s_score,sc2.s_score from score sc1,score sc2 left join student st on st.s_id = sc2.s_id where sc1.s_id = sc2.s_id and sc1.s_score>sc2.s_score and sc1.c_id = '01' and sc2.c_id = '02' 

-- 2、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 st.s_id,st.s_name,AVG(s_score) as avg_score from score sc inner join student st on sc.s_id = st.s_id  group by st.s_id,st.s_name having AVG(s_score)>=60;

-- 3、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 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 b.s_id,b.s_name,0 as avg_score from student b where b.s_id not in (select s_id from score);


-- 4、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 选课总数 ,sum(b.s_score) as 总分 from student a
	 left join score b on a.s_id = b.s_id group by a.s_id,a.s_name ;

-- 5、查询"李"姓老师的数量 

select count(*) as 李姓老师数量 from teacher where t_name like '李%';


-- 6、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.c_id from course c 
join teacher d on c.t_id = d.t_id where d.t_name = '张三'); 

-- 7、查询没学过"张三"老师授课的同学的信息

select distinct a.* from student a join score b on a.s_id = b.s_id where b.s_id not in (select s_id from score where c_id =(select c.c_id from course c 
join teacher d on c.t_id = d.t_id where d.t_name = '张三')); 

-- 8、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 * from student where s_id in 
	(select a.s_id from score a join score b on a.s_id = b.s_id
		 where a.c_id = '01' and b.c_id = '02');

-- 9、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 * from student where s_id in 
	(select s_id from score where c_id = '01' )
		and s_id not in (select s_id from score where c_id = '02' );

-- 10、查询没有学全所有课程的同学的信息 
select * from student where s_id not in 
	(select s_id from score group by s_id having count(c_id) = 3);

-- 11、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 distinct a.* from student a left join score b on a.s_id = b.s_id where b.c_id in
	(select c_id from score where s_id = '01') and a.s_id != '01'  ;

-- 12、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 * from student where s_id in 
	(select s_id from score group by s_id having count(c_id) = 
		(select count(c_id) from score where s_id = '01') and s_id not in 
			(select s_id from score where c_id not in 
				(select c_id from score where s_id = '01')) and s_id != '01');

-- 13、查询没学过"张三"老师讲授的任一门课程的学生姓名
select s_name from student where s_id not in 
	(select s_id from score where c_id  in 
		(select c_id from course where t_id in 
			(select t_id from teacher where t_name ='张三')));

-- 14、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 ,b.s_name,round(avg(a.s_score),2) as 平均成绩 from score a
	 left join student b on a.s_id = b.s_id 
	 	where s_score < 60 group by a.s_id,b.s_name having count(1) >=2;

-- 15、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 
	left join score b  on a.s_id = b.s_id 
		where b.c_id = '01' and b.s_score < 60 
			order by  b.s_score desc;

-- 16、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_name ,
sum(case when b.c_id = '01' then s_score else null end ) as 语文,
sum(case when b.c_id = '02' then s_score else null end ) as 数学,
sum(case when b.c_id = '03' then s_score else null end ) as 英语,
round(avg(s_score),2) as 平均成绩
from student a left join score b on a.s_id = b.s_id group by a.s_name
order by 平均成绩 desc;


-- 17.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：>=90
select b.c_id,b.c_name,
max(a.s_score) as 最高分,
min(a.s_score) as 最低分,
round(avg(a.s_score),2) as 平均分, 
round(sum(case when a.s_score>= 60 then 1 else 0 end)/count(s_id),2) as 及格率 ,
round(sum(case when a.s_score>= 70 and a.s_score <80 then 1 else 0 end)/count(s_id),2) as 中等率,
round(sum(case when a.s_score>= 80 and a.s_score <90 then 1 else 0 end)/count(s_id),2) as 优良率,
round(sum(case when a.s_score>= 90 then 1 else 0 end)/count(s_id),2) as 优秀率
 from score a left join course b on a.c_id = b.c_id group by b.c_id,b.c_name;
 
-- 18、按各科成绩进行排序，并显示排名

select  sc.s_id ,st.s_name,sc.c_id,sc.s_score,RANK() OVER (partition by c_id ORDER BY s_score DESC ) AS rank  from score sc
			left join student st on sc.s_id = st.s_id
			group by sc.s_id,st.s_name,sc.c_id,sc.s_score order by sc.c_id,sc.s_score desc;

-- 19、查询学生的总成绩并进行排名

select RANK() OVER (ORDER BY sum(s_score) DESC ) AS rank , s_id ,sum(s_score) as 总成绩  from score 
			group by s_id order by sum(s_score) desc;

-- 20、查询不同老师所教不同课程平均分从高到低显示 
select a.c_id, d.t_name,round(avg(a.s_score),2) as 平均分 from score a 
	left join student b on a.s_id = b.s_id
	left join course c on a.c_id = c.c_id 
	left join teacher d on c.t_id = d.t_id group by a.c_id,d.t_name
	order by 平均分 desc;