在执行 concat_ws 和 collect_list 后，Hive Coalesce 函数未返回预期结果

Question

我需要在 table 服务中转换列 servicename，然后合并值。

services:
userid servicename
1      A
2      B
2      C
3      B
1      C
4
5      C

我正在尝试的查询是

SELECT userid,
       COALESCE(a,b,c) AS servicename
FROM (SELECT userid,
             concat_ws('',a) AS a,
             concat_ws('',b) AS b,
             concat_ws('',c) AS c
      FROM (SELECT userid,
                   collect_list(a.group_map['A']) AS a,
                   collect_list(a.group_map['B']) AS b,
                   collect_list(a.group_map['C']) AS c
            FROM (SELECT userid,
                         MAP(servicename,servicename) AS group_map
                  FROM (SELECT userid, servicename, servicename FROM services) AS table1) AS table2) AS table3) AS table4

这里是每个 SELECT 查询的细目及其结果：

查询 1：

SELECT userid,
       servicename,
       servicename
FROM services

结果 1：

userid servicename servicename
   1      A           A
   2      B           B
   2      C           C
   3      B           B
   1      C           C
   4 
   5      C           C

查询 2：

SELECT userid,
       MAP(servicename,servicename) AS group_map
FROM table1

结果 2：

userid    group_map
    1      {"A":"A"}
    2      {"B":"B"}
    2      {"C":"C"}
    3      {"B":"B"}
    1      {"C":"C"}
    4      {"null":"null"}
    5      {"C":"C"}

查询 3：

SELECT userid,
       collect_list(a.group_map['A']) AS a,
       collect_list(a.group_map['B']) AS b,
       collect_list(a.group_map['C']) AS c
FROM table2

结果 3：

userid    a      b      c
1       ["A"]         ["C"]
2              ["B"]  ["C"]
3              ["B"]
4           
5                     ["C"]

下面的concat_ws函数是将数组转String

查询 4：

SELECT userid,
       concat_ws('',a) AS a,
       concat_ws('',b) AS b,
       concat_ws('',c) AS c
FROM table3

结果 4：

userid    a    b   c
1         A        C
2              B   C
3              B
4           
5                  C

最后在查询中使用 COALESCE 函数得到如下结果：

查询 5

SELECT userid,
       COALESCE(a,b,c) AS servicename
FROM table4

下面是我希望看到的结果

结果 5：

userid  servicename
1       A
2       B
3       B
4
5       C

但是，我只得到 Service A 或 null，如下所示：

userid  servicename
    1       A
    2       
    3       
    4
    5

有人怀疑有什么问题吗？是否需要铸造？

我一直在尝试不同的东西，也尝试在网上搜索，但还没有成功。

提前致谢！

Answer 1

看起来您只需要每个 ID 的 1 个服务名称

select * from 
(
     select userid,servicename,row_number() over (partition by userid order by servicename) as row_no 
) res
where res.row_no = 1

这应该让你

userid  servicename
1       A
2       B
3       B
4
5       C

如果您尝试为每个用户 ID 转换服务名称

select userid, collect_set(servicename)
from table
group by userid;

这应该让你

userid  servicename
1       A,C
2       B,C
3       B
4
5       C

在执行 concat_ws 和 collect_list 后，Hive Coalesce 函数未返回预期结果

Hive Coalesce function isn't returning expected results after performing concat_ws and and collect_list

mysql

hadoop

hive

coalesce