如何在 BigQuery SQL 中添加 arrays？

Question

我有一个 UDF，它为表的每一行返回一个相同大小的浮点数组。 如何求和这些 arrays 的值？

换句话说，我该怎么做：

create temp function f(...)
returns array<float64>
...;
select sum(f(column)) from table

作为此操作的结果，我需要获得另一个大小相等的数组，其中

result[i] = sum(over rows) f(row, column)[i]

Answer 1

因此，根据您的评论，您要查找的是所有数组的值之sum 。 这是使用UNNEST运算符的方法

WITH mydata  AS (
  SELECT [1.4, 1.3, 1.4, 1.1] as myarray
  union all 
  SELECT [1.4, 1.3, 1.4, 1.1] as myarray
  union all 
  SELECT [1.4, 1.3, 1.4, 1.1] as myarray
)

SELECT SUM(eachelement) from mydata, UNNEST(myarray) AS eachelement; 

Answer 2

这是一个使用ANY TYPE的函数，以支持对FLOAT64 ， INT64或NUMERIC数组以及一些示例输入进行求和：

CREATE TEMP FUNCTION ElementWiseSum(arr1 ANY TYPE, arr2 ANY TYPE) AS (
  ARRAY(SELECT x + arr2[OFFSET(off)] FROM UNNEST(arr1) AS x WITH OFFSET off ORDER BY off)
);

SELECT arr1, arr2, ElementWiseSum(arr1, arr2) AS result
FROM (
  SELECT [1, 2, 3] AS arr1, [4, 5, 6] AS arr2 UNION ALL
  SELECT [7, 8], [9, 10] UNION ALL
  SELECT [], [] UNION ALL
  SELECT [11, 12, 13, 14, 15], [16, 17, 18, 19, 20]
);

它使用WITH OFFSET取消嵌套arr1 ，然后使用此偏移量从arr2检索等效元素，并按该偏移量排序以确保保留元素顺序。

编辑：要对各行求和，可以对数组进行嵌套，计算按元素偏移量分组的总和，然后将总和重新聚集到新数组中：

SELECT
  ARRAY_AGG(sum ORDER BY off) AS arr
FROM (
  SELECT
    off,
    SUM(x) AS sum
  FROM (
    SELECT [1, 2, 3] AS arr UNION ALL
    SELECT [7, 8, 9] UNION ALL
    SELECT [4, 5, 6] UNION ALL
    SELECT [10, 11, 12]
  ), UNNEST(arr) AS x WITH OFFSET off
  GROUP BY off
);

Answer 3

如果定义了UDF（在您的列中输入并返回预定（或固定）尺寸的float64数组），则可以使用简化的解决方案。 例如，对于3维数组，类似：

create temp function f(...)
returns array<float64>
...;

with dataset as (
  select arr[offset(0)] as col_a, arr[offset(1)] as col_b, arr[offset(2)] as col_c
    from (
       select f(mycolumn) as arr
       from `mydataset.mytable`
    )
)

select [sum(col_a), sum(col_b), sum(col_c)] as new_array from dataset

Answer 4

这并没有直接回答 OP 的问题，但是人们登陆此页面搜索“如何在 BigQuery SQL 中添加 arrays？” 可能会受益。

（基于@elliott-brossard 答案编辑）如果您有 2 个 arrays，但 1 个数组包含一个结构，您可以使用以下代码将它们加在一起：

WITH mydata AS (
  SELECT
    [1, 2, 3] AS arr
    -- ,[7, 8, 9] AS arr2
    ,[
      STRUCT(7 AS timeOnSite)
      ,STRUCT(8 AS timeOnSite)
      ,STRUCT(9 AS timeOnSite)
    ] AS arr2
)

SELECT
  (
    SELECT
      ARRAY_AGG(sum ORDER BY off) AS arr
    FROM (
      SELECT
        off,
        SUM(x) AS sum
      FROM (
        SELECT arr UNION ALL
        -- SELECT arr2
        SELECT (SELECT ARRAY_AGG(t.timeOnSite) FROM UNNEST(arr2) AS t)
      ), UNNEST(arr) AS x WITH OFFSET off
      GROUP BY off
    )  
  ) AS sum_arrays
FROM 
  mydata