这是在网上看了别人的练习题,自己练了一遍,把其中比较好的拎了出来。
insert into t_user (id,name,code,time) values((select(select max(b.id)+1 from t_user b)),"CGLIB",2,now());
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(3),
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');
insert into Student values('09' , '李心草','1996-10-18' , '女');
insert into Student values('10' , '张燕' , '2001-11-22' , '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');
insert into Course values('04' , '物理' , '04');
insert into Course values('05' , '地理' , '05');
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');
insert into Teacher values('04' , '朱六');
insert into Teacher values('05' , '田七');
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('09' , '03' , 98);
insert into Score values('07' , '04' , 88);
insert into Score values('09' , '05' , 89);
insert into Score values('10' , '04' , 65);
insert into Score values('10' , '05' , 57);
-- *****
1、查询和"01"号同学课程完全相同的其他同学的信息
之所以把难的放在第一位,就是想说,没必要死磕钻牛角尖,开发中遇到这种情况,就Java代码结合SQL就简单很多了。
-- ****
2、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,不及格率,及格率,优良率
只能用sum(case when then else end)語法,count怎末搞都不行
select c.c_id,c.c_name as name ,max(s.s_score)as zg,min(s.s_score)as zd,avg(s.s_score)as pj
,100*(sum(case when s.s_score<60 then 1 else 0 end)/sum(case when s.s_score then 1 else 0 end)) as 不及格
,100*(sum(case when s.s_score>=60 and s.s_score< 80 then 1 else 0 end)/sum(case when s.s_score then 1 else 0 end ))as 及格
,100*(sum(case when s.s_score>=80 then 1 else 0 end)/sum(case when s.s_score then 1 else 0 end))as 优良
from score s left join course c on s.c_id=c.c_id group by s.c_id ;
-- ****
3、统计各科成绩各分数段人数:课程编号,课程名称,[100-80],[80-60],[60-00]及所占百分比
用到distinct去重,視圖等
select distinct r.c_id,r.c_name,A.`<=60`,A.`百分比`,B.`60-80`,B.`百分比`,C.`>=80`,C.`百分比` from score s
left join
(select o.c_id,sum(case when o.s_score<60 then 1 else 0 end)as '<=60',
100*sum(case when o.s_score<60 then 1 else 0 end)/sum(case when o.s_score then 1 else 0 end) as '百分比'
from score o group by o.c_id) as A on s.c_id= A.c_id
left join
(select o.c_id,sum(case when o.s_score>=60 and o.s_score<80 then 1 else 0 end)as '60-80',
100*sum(case when o.s_score>=60 and o.s_score<80 then 1 else 0 end)/sum(case when o.s_score then 1 else 0 end) as '百分比'
from score o group by o.c_id) as B on s.c_id=B.c_id
left join
(select o.c_id,sum(case when o.s_score>80 then 1 else 0 end) as '>=80',
100*sum(case when o.s_score>80 then 1 else 0 end)/sum(case when o.s_score then 1 else 0 end) as '百分比'
from score o group by o.c_id)as C on s.c_id=C.c_id
left join course r on s.c_id=r.c_id;
-- ***
4、查询"01"课程比"02"课程成绩高的学生的信息及课程分数
同一表进行不同字段比较
select t.s_name,s.s_score
from student t left join score s on t.s_id=s.s_id and s.c_id='01' left join score c on t.s_id=c.s_id and c.c_id='02'
where s.s_score>c.s_score;
-- *
5、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
AVG函数
select t.s_id,t.s_name,avg(s.s_score) as pj from student t left join score s on t.s_id=s.s_id group by t.s_id having pj>='60';
-- *
6、查询不同老师所教不同课程平均分从高到低显示
select e.t_id,e.t_name,avg(s.s_score) as pj from teacher e ,course c, score s
where e.t_id=c.t_id and c.c_id=s.c_id group by e.t_id order by pj desc;
-- *
7、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
count+sum函数
select t.s_id,t.s_name,count(s.s_id) as numbs,sum(s.s_score) from student t left join score s on t.s_id=s.s_id group by t.s_id;
-- *
8、查询学过"张三"老师授课的同学的信息
inner join链接
select t.s_name,t.s_sex,c.c_name,e.t_name
from student t inner join score s on t.s_id=s.s_id
inner join course c on s.c_id=c.c_id
inner join teacher e on c.t_id=e.t_id
where e.t_name="张三";
-- **
9、查询没学过"张三"老师授课的同学的信息
not in与inner join
select * from student t where t.s_id not in (
select s.s_id from score s inner join course c on s.c_id=c.c_id
inner join teacher e on c.t_id=e.t_id
where e.t_name="张三" );
-- **
10、查询学过编号为"01"、"02"的课程的同学的信息
查同一字段多个情况,消除笛卡尔积。
select t.* from student t ,score s,score c
where t.s_id=s.s_id and s.c_id='01'
and s.s_id=c.s_id and c.c_id='02';
-- *
11、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 t.* from student t,score s
where t.s_id=s.s_id and s.c_id=01
and t.s_id not in (select c.s_id from score c where c.c_id=02);
-- *
12、查询没有学全所有课程的同学的信息
select t.* from student t left join score s on t.s_id=s.s_id
group by t.s_id having count(s.s_score)<(select count(*) from course);
-- ***
13、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
in函数 group by分组去除笛卡尔积
select * from student t where t.s_id
in (select o.s_id from score o where o.c_id
in(select s.c_id from score s where s.s_id =01) group by o.s_id);
用distinct函数去除重复
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')
);
-- **
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
where后面还能group by,group by后面加条件必须having。avg、sum需group by分组。
select t.s_name,round(avg(o.s_score)) from student t left join score o on t.s_id=o.s_id
where t.s_id in (select s.s_id from score s where s.s_score<60 group by s.s_id having count(s.s_score)>=2)
group by t.s_id;
-- ***
15、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 t.s_id,t.s_name,(select o.s_score from score o where t.s_id=o.s_id and o.c_id='01') yw
,(select o.s_score from score o where t.s_id=o.s_id and o.c_id='02') sx
,(select o.s_score from score o where t.s_id=o.s_id and o.c_id='03') yy
,round(avg(s.s_score),1) pj
from student t left join score s on t.s_id=s.s_id group by t.s_id order by pj desc
-- *
16、查询出只有两门课程的全部学生的学号和姓名
select t.s_id,t.s_name from student t join score s on t.s_id=s.s_id group by t.s_id having count(s.s_score)=2
-- ***
17、查询各学生的年龄
select t.s_id,t.s_name,t.s_birth,
(date_format(now(),"%Y")-date_format(t.s_birth,"%Y")-(case when (date_format(now(),"%m%d")>date_format(t.s_birth,"%m%d"))then 0 else 1 end))as age
from student t ;
-- *
18、查询本周过生日的学生
select * from student t where week(date_format(now(),'%Y%m%d'))=week(t.s_birth);
-- *
19、查询本月过生日的学生
select * from student t where MONTH(date_format(now(),'%Y%m%d')) =month(t.s_birth);