Question

我正在寻找聚合函数的sql模式来聚合数组。如果我有2行：

select id, *aggregate_function*(array)
from table
group by id

我想做以下事情：

|id | *aggregate_function* | |-----+-----------------------| |1 | [1,2,3,4,5,6,7,8] | |-----------------------------|

我希望结果是：

sublime_plugin.py

没有本地postgres功能可以执行此聚合。但也许有sql模式可以在这里使用？

Answer 1

这样的事情应该有效：

with mytable as
(
select 1 as id, array[1, 2, 3, 4] as myarray

union all

select 1 as id, array[5, 6] as myarray

union all 

select 1 as id, array[7, 8] as myarray
)

select
  id,
  array_agg(elements order by elements)
from mytable, unnest(myarray) as elements
group by id

有关于在此处构建自定义函数的一些讨论：Concatenate/merge array values during grouping/aggregation

Answer 2

您可以取消，然后分组：

WITH x (id, arr) AS (
  VALUES 
    (1, ARRAY[1,2,3,4])
  , (1, ARRAY[5,6])
  , (1, ARRAY[7, 8])
)
SELECT id, ARRAY_AGG(splitup) 
FROM (
    SELECT 
        id
      , unnest(arr) splitup 
    FROM x) splitup
GROUP BY 1

postgresql将数组聚合到一个具有所有元素的联合的数组中

2 个答案: