hive 行列转换案例

0  stu表数据:

stu:
id             name
hello,you zm2008
hello,me zm2015

1 实现单词计数:     (列转行)   ---> split切分+explode(炸开)

1.0 数据拆分成数组

select split(id,',') from  stu;    得到数组
[hello,you]
[hello,me]

1.1 继续将数组拆分(hive explode函数会将数组继续拆分成单个字符)

select explode(split(id,','))  from stu;   窗体函数
hello
you
hello
me

1.2 分组统计:

select t1.c1, count(1) from (select explode(split(id,',')) as c1  from stu)  t1 group by t1.c1;
hello 2
you 1
me 1

上述语句中, t1表是1.1的结果

2  行转列:  明确以哪个字段分组,分组后将列转成行使用  

--->  多列间隔符concat_ws+封装多列组合体 collect_set+ 分组字段 grtoup by

公式: concat_ws(",",collect_set(要转成行的列))  group by 分组列

2.0 表数据

列转换行：

user
id name
1 zhangsan
2 lisi
3 wangwuaddress
name     addr
zhangsan beijing
zhangsan shanghai
lisi tianjin
wangwu nanjing

期待结果:
1 zhangsan beijing,shanghai
2 lisi tianjin
3 wangwu nanjing

2.1  函数介绍：

collect_set(x)   列转行函数---没有重复， 组装多列的数据的结构体
collect_list(x)   列转行函数---可以有重复，组装多列的数据的结构体
concat_ws 拼接函数， 用于多列转成同一行字段后，间隔符

2.2 操作步骤:

2.2.0:

select user.id, user.name, address.addr from user join address on user.name = address.name;

1 zhangsan beijing
2 zhangsan shanghai
3 lisi tianjin
4 wangwu nanjing

2.2.1:

select max(user.id), user.name, collect_set(address.addr) from user join address on user.name = address.name group by user.name;
2 lisi [tianjin]

3 wangwu [nanjing]
1 zhangsan [shanghai,beijing]

2.2.2: 以name分组,将name相同下的 addr列转变成行存储,并且分组后列为多个下下以,做间隔

select max(user.id) as id, user.name, concat_ws(",",collect_set(address.addr)) from user join address on user.name = address.name group by user.name order by id;

1 zhangsan shanghai,beijing
2 lisi tianjin
3 wangwu nanjing

2.3 多行转换一列案例2：

一、问题

hive如何将

a       b       1
a       b       2
a       b       3
c       d       4
c       d       5
c       d       6

变为：

a       b       1,2,3
c       d       4,5,6


二、数据

test.txt

a       b       1 
a       b       2 
a       b       3 
c       d       4 
c       d       5 
c       d       6

三、答案

1.建表

drop table tmp_jiangzl_test;
create table tmp_jiangzl_test
(
col1 string,
col2 string,
col3 string
)
row format delimited fields terminated by '\t'
stored as textfile;


load data local inpath '/home/jiangzl/shell/test.txt' into table tmp_jiangzl_test;

2.处理

select col1,col2,concat_ws(',',collect_set(col3)) 
from tmp_jiangzl_test  
group by col1,col2;

3 行转换列：  查询多个字段下 later view的使用

行转列中，如果查询字段是多个，不仅仅是列转行的这个字段的话，那么久要是用到 later view注意later view后要有别名

1    zhangsan    shanghai,beijing

2    lisi    tianjin

3    wangwu    nanjing

create table stu(id string,name string,addr string) row format delimited fields terminated by '\t'; 
  
 
  

      
  
 
  

    load data local inpath '/home/18511893257/stu' into table stu; 
  
 
  

      
  
 
  

    select id, name, addr1  from stu  lateral view explode(split(addr,','))a as addr1;

OK

1       zhangsan        shanghai

1       zhangsan        beijing

2       lisi    tianjin

3       wangwu  nanjing

 4 行转换列：  单表下写法

hive如何将

a       b       1
a       b       2
a       b       3
c       d       4
c       d       5
c       d       6

变为：

a       b       1,2,3
c       d       4,5,6

select col1,col2,concat_ws(',',collect_set(col3)) 
from tmp_jiangzl_test  
group by col1,col2;    ----------------》 已经验证过  OK