hive 之 Cube, Rollup介绍
1. GROUPING SETS
GROUPING SETS作为GROUP BY的子句,允许开发人员在GROUP BY语句后面指定多个统维度,可以简单理解为多条group by语句通过union all把查询结果聚合起来结合起来。
为方便理解,以testdb.test_1为例:
hive> use testdb;
hive> desc test_1;
user_id string id
device_id string 设备类型:手机、平板
os_id string 操作系统类型:ios、android
app_id string 手机app_id
client_v string 客户端版本
channel string 渠道
grouping sets语句 | 等价hive语句 |
---|---|
select device_id,os_id,app_id,count(user_id) from test_1 group by device_id,os_id,app_id grouping sets((device_id)) | SELECT device_id,null,null,count(user_id) FROM test_1 group by device_id |
select device_id,os_id,app_id,count(user_id) from test_1 group by device_id,os_id,app_id grouping sets((device_id,os_id)) | SELECT device_id,os_id,null,count(user_id) FROM test_1 group by device_id,os_id |
select device_id,os_id,app_id,count(user_id) from test_1 group by device_id,os_id,app_id grouping sets((device_id,os_id),(device_id)) | SELECT device_id,os_id,null,count(user_id) FROM test_1 group by device_id,os_id UNION ALL SELECT device_id,null,null,count(user_id) FROM test_1 group by device_id |
select device_id,os_id,app_id,count(user_id) from test_1 group by device_id,os_id,app_id grouping sets((device_id),(os_id),(device_id,os_id),()) | SELECT device_id,null,null,count(user_id) FROM test_1 group by device_id UNION ALL SELECT null,os_id,null,count(user_id) FROM test_1 group by os_id UNION ALL SELECT device_id,os_id,null,count(user_id) FROM test_1 group by device_id,os_id UNION ALL SELECT null,null,null,count(user_id) FROM test_1 |
2. CUBE函数
cube简称数据魔方,可以实现hive多个任意维度的查询,cube(a,b,c)则首先会对(a,b,c)进行group by,然后依次是(a,b),(a,c),(a),(b,c),(b),(c),最后在对全表进行group by,cube会统计所选列中值的所有组合的聚合
select device_id,os_id,app_id,client_v,channel,count(user_id)
from test_1
group by device_id,os_id,app_id,client_v,channel with cube;
等价于:
SELECT device_id,null,null,null,null ,count(user_id) FROM test_1 group by device_id
UNION ALL
SELECT null,os_id,null,null,null ,count(user_id) FROM test_1 group by os_id
UNION ALL
SELECT device_id,os_id,null,null,null ,count(user_id) FROM test_1 group by device_id,os_id
UNION ALL
SELECT null,null,app_id,null,null ,count(user_id) FROM test_1 group by app_id
UNION ALL
SELECT device_id,null,app_id,null,null ,count(user_id) FROM test_1 group by device_id,app_id
UNION ALL
SELECT null,os_id,app_id,null,null ,count(user_id) FROM test_1 group by os_id,app_id
UNION ALL
SELECT device_id,os_id,app_id,null,null ,count(user_id) FROM test_1 group by device_id,os_id,app_id
UNION ALL
SELECT null,null,null,client_v,null ,count(user_id) FROM test_1 group by client_v
UNION ALL
SELECT device_id,null,null,client_v,null ,count(user_id) FROM test_1 group by device_id,client_v
UNION ALL
SELECT null,os_id,null,client_v,null ,count(user_id) FROM test_1 group by os_id,client_v
UNION ALL
SELECT device_id,os_id,null,client_v,null ,count(user_id) FROM test_1 group by device_id,os_id,client_v
UNION ALL
SELECT null,null,app_id,client_v,null ,count(user_id) FROM test_1 group by app_id,client_v
UNION ALL
SELECT device_id,null,app_id,client_v,null ,count(user_id) FROM test_1 group by device_id,app_id,client_v
UNION ALL
SELECT null,os_id,app_id,client_v,null ,count(user_id) FROM test_1 group by os_id,app_id,client_v
UNION ALL
SELECT device_id,os_id,app_id,client_v,null ,count(user_id) FROM test_1 group by device_id,os_id,app_id,client_v
UNION ALL
SELECT null,null,null,null,channel ,count(user_id) FROM test_1 group by channel
UNION ALL
SELECT device_id,null,null,null,channel ,count(user_id) FROM test_1 group by device_id,channel
UNION ALL
SELECT null,os_id,null,null,channel ,count(user_id) FROM test_1 group by os_id,channel
UNION ALL
SELECT device_id,os_id,null,null,channel ,count(user_id) FROM test_1 group by device_id,os_id,channel
UNION ALL
SELECT null,null,app_id,null,channel ,count(user_id) FROM test_1 group by app_id,channel
UNION ALL
SELECT device_id,null,app_id,null,channel ,count(user_id) FROM test_1 group by device_id,app_id,channel
UNION ALL
SELECT null,os_id,app_id,null,channel ,count(user_id) FROM test_1 group by os_id,app_id,channel
UNION ALL
SELECT device_id,os_id,app_id,null,channel ,count(user_id) FROM test_1 group by device_id,os_id,app_id,channel
UNION ALL
SELECT null,null,null,client_v,channel ,count(user_id) FROM test_1 group by client_v,channel
UNION ALL
SELECT device_id,null,null,client_v,channel ,count(user_id) FROM test_1 group by device_id,client_v,channel
UNION ALL
SELECT null,os_id,null,client_v,channel ,count(user_id) FROM test_1 group by os_id,client_v,channel
UNION ALL
SELECT device_id,os_id,null,client_v,channel ,count(user_id) FROM test_1 group by device_id,os_id,client_v,channel
UNION ALL
SELECT null,null,app_id,client_v,channel ,count(user_id) FROM test_1 group by app_id,client_v,channel
UNION ALL
SELECT device_id,null,app_id,client_v,channel ,count(user_id) FROM test_1 group by device_id,app_id,client_v,channel
UNION ALL
SELECT null,os_id,app_id,client_v,channel ,count(user_id) FROM test_1 group by os_id,app_id,client_v,channel
UNION ALL
SELECT device_id,os_id,app_id,client_v,channel ,count(user_id) FROM test_1 group by device_id,os_id,app_id,client_v,channel
UNION ALL
SELECT null,null,null,null,null ,count(user_id) FROM test_1
3. ROLL UP函数
rollup可以实现从右到左递减多级的统计,显示统计某一层次结构的聚合
select device_id,os_id,app_id,client_v,channel,count(user_id)
from test_1
group by device_id,os_id,app_id,client_v,channel with rollup;
等价于:
select device_id,os_id,app_id,client_v,channel,count(user_id)
from test_1
group by device_id,os_id,app_id,client_v,channel
grouping sets ((device_id,os_id,app_id,client_v,channel),(device_id,os_id,app_id,client_v),(device_id,os_id,app_id),(device_id,os_id),(device_id),());
4.Grouping_ID函数
当我们没有统计某一列时,它的值显示为null,这可能与列本身就有null值冲突,这就需要一种方法区分是没有统计还是值本来就是null。(写一个排列组合的算法,就马上理解了,grouping_id其实就是所统计各列二进制和)
例子如下:
Column1 (key) | Column2 (value) |
---|---|
1 | NULL |
1 | 1 |
2 | 2 |
3 | 3 |
3 | NULL |
4 | 5 |
hql统计:
SELECT key, value, GROUPING_ID, count(*) from T1 GROUP BY key, value WITH ROLLUP
结果如下:
key | value | GROUPING_ID | count(*) |
---|---|---|---|
NULL | NULL | 0 00 | 6 |
1 | NULL | 1 10 | 2 |
1 | NULL | 3 11 | 1 |
1 | 1 | 3 11 | 1 |
2 | NULL | 1 10 | 1 |
2 | 2 | 3 11 | 1 |
3 | NULL | 1 10 | 2 |
3 | NULL | 3 11 | 1 |
3 | 3 | 3 11 | 1 |
4 | NULL | 1 10 | 1 |
4 | 5 | 3 11 | 1 |
GROUPING_ID转变为二进制,如果对应位上有值为null,说明这列本身值就是null。(通过类DataFilterNull.py 扫描,可以筛选过滤掉列中null、“”统计结果),
5. 窗口函数
hive窗口函数,感觉大部分都是在模仿oracle,有对oracle熟悉的,应该看下就知道怎么用。
具体参见:http://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.0.0.2/ds_Hive/language_manual/ptf-window.html
参考文章
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