HIVE实验 | 易学教程

Hive基本操作实验

show命令显示数据库和表
```
show databases;
show tables;
```
create创建test数据库，并通过show命令查看。
```
create database test;
show database;
```

create命令创建emp表，列名分别为empno、ename、deptno、mgr、和salary，并通过show命令查看。

create table emp(empno string,ename string,deptno string,mgr string,salary int) row format delimited fields terminated by '\t';

show tables;

将/root下面的emp.txt中的内容导入到emp表，数据之间以\t分隔开。

load data local inpath '/root/emp.txt' overwrite into table emp；

select * from emp；
向emp表增加列adress，然后显示emp表的结构；

alter table emp add columns (adress string);

desc emp;
建立以firstname为分区列的分区表testa；向分区表testa中插入数据，然后查看目录结构。

create table testa(sno string,sname string,ssex,string,sage int) partition by (firstname string);

insert into testa partition (firstname='east') select empno,ename,'male',30 from emp;

insert into testa partiton (firstname='west') select empno,ename,'female',28 from emp;
创建表empt

create table empt as select * from emp;

desc emp2;

select * from emp2;
向empt表中插入几条数据，并将empt重命名为empa;

insert into empt() values();

insert into empt() values();

alter table empt rename ro empa;
将empa的数据写入到本地目录。

insert overwrite local diretory 'empa' row format delimited fields terminated by '\t' select * from empa;
将表empa导出。

export table empa to '/exportdir/empa';

删除empa，将empa导入时改名为empb，并查看信息和内容。

drop table empa;
import table empb from '/exportdir/empa';
dsc empb;
select * from empb;

定义外部表

create external table employee (empno string,ename string,deptno string,mgr string,salary int) row fromat delimited fileds terminated by '\t' location '/hive/warehose/emp'

Hive综合查询

统计学生总人数和平均年龄
```
select count(1),avg(age) from student;
```

查询每个系的男生人数

select dept,count(1) from student where sex='男' group by dept;

查询每个学生的学号、选修课程数和平均成绩。

select s.sname,tmp.cnt,tmp.avg_grade from student s,(select sno,count(1) cnt,avg(grade) avg_grade from sc group by sno) tmp where s.sno=tmp.sno;

查询选修了3门以上客户曾的学生学号、选修课程数和平均成绩

hive> select sno,count(1) cnt,avg(grade) avg_grade from sc group by sno having count(1) >3;

查询每个学生的学号、姓名、课程号、课程名和成绩。

select s.sno,s.sname,sc.cno,c.cname,sc.grade from student s join sc on s.sno=sc.sno join course c on sc.cno=c.cno;

查询学生学号，要求每门课程都在85分以上。

select sno from sc group by sno having min(grade) > 80;

查询学了1号课，没学2号课的学生学号。

select distinct t1.sno from (select sno from sc where cno=1) t1 where not exists(select sno from sc where cno=2 and sno=t1.sno);

select t1.sno from (select sno from sc where cno=1) t1 left outer join  (select sno from sc where cno=2) t2 on t1.sno=t2.sno where t2.sno is null;

查询考试成绩大于所属课程平均成绩的学号、课程号和成绩。

select sc.* from sc,(select cno,avg(grade) avg_grade from sc group by sno) tmp where sc.cno=tmp.cno and sc.grade > tmp.avg_grade;

查询已选课的学生的信息.

select * from student where sno in(select distinct sno from sc);

查询学生的学生学号、姓名、课程号和成绩，包括那些没有选课的学生

select s.sno,s.sname,sc.cno,sc.grade from student s left outer join sc on
s.sno =sc.sno;

查询平均成绩最高的课程号

select cno,avg(grade) avg_grade from sc group by cno order by avg_grade desc limit 1;

查询与学号为15001学生有共同选修课的学生学号。

select sno from sc where sno not in
(select sno from sc where cno not in(select cno from sc where sno='15001'))
and sno<>'15001' group by sno having count(1) = (select count(*) from sc where sno='15001')

来源：CSDN

作者：weixin_42534356

链接：https://blog.csdn.net/weixin_42534356/article/details/103855860

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emp

Hive