Question

例如，我在下面有一张桌子

+-----------+-------+------------+
|        Id |      a|           b|
+-----------+-------+------------+
|         1 |     6 |         20 |
|         1 |     4 |         55 |
|         1 |     9 |         56 |
|         1 |     2 |         67 |
|         1 |     7 |         80 |
|         1 |     5 |         66 |
|         1 |     3 |         33 |
|         1 |     8 |         34 |
|         1 |     1 |         52 |

我希望使用Impala输出如下所示

+-----------+-------------------+-----------------------------+
|        Id |     a             |                           b |
+-----------+-------------------+-----------------------------+
|         1 | 6,4,9,2,7,5,3,8,1 | 20,55,56,67,80,66,33,34,52  |
+-----------+-------------------+-----------------------------+

在Impala中，我已使用

SELECT Id, 
       group_concat(DISTINCT a) AS a, 
       group_concat(DISTINCT b) AS b 
FROM table GROUP BY Id

它总是会出现语法错误。只是想知道是否不允许在Impala中对一个查询使用multi group_concat？还是不允许对一个查询使用多个Distinct？

Answer 1

来自documentation for GROUP_CONCAT：

您不能将DISTINCT运算符应用于此函数的参数。

但是，作为解决方法，我们可以使用两个单独的子查询来查找不同的值：

WITH cte1 AS (
    SELECT Id, GROUP_CONCAT(a) AS a
    FROM (SELECT DISTINCT Id, a FROM yourTable) t
    GROUP BY Id
),
cte2 AS (
    SELECT Id, GROUP_CONCAT(b) AS b
    FROM (SELECT DISTINCT Id, b FROM yourTable) t
    GROUP BY Id
)

SELECT
    t1.Id,
    t1.a,
    t2.b
FROM cte1 t1
INNER JOIN cte2 t2
    ON t1.Id = t2.Id;

Impala-Impala是否在一个查询中允许多个GROUP_CONCAT

1 个答案: