[英]How do I add arrays in BigQuery SQL?
我有一個 UDF,它為表的每一行返回一個相同大小的浮點數組。 如何求和這些 arrays 的值?
換句話說,我該怎么做:
create temp function f(...)
returns array<float64>
...;
select sum(f(column)) from table
作為此操作的結果,我需要獲得另一個大小相等的數組,其中
result[i] = sum(over rows) f(row, column)[i]
因此,根據您的評論,您要查找的是所有數組的值之sum
。 這是使用UNNEST
運算符的方法
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;
這是一個使用ANY TYPE
的函數,以支持對FLOAT64
, INT64
或NUMERIC
數組以及一些示例輸入進行求和:
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
,然后使用此偏移量從arr2
檢索等效元素,並按該偏移量排序以確保保留元素順序。
編輯:要對各行求和,可以對數組進行嵌套,計算按元素偏移量分組的總和,然后將總和重新聚集到新數組中:
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
);
如果定義了UDF(在您的列中輸入並返回預定(或固定)尺寸的float64
數組),則可以使用簡化的解決方案。 例如,對於3維數組,類似:
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
這並沒有直接回答 OP 的問題,但是人們登陸此頁面搜索“如何在 BigQuery SQL 中添加 arrays?” 可能會受益。
(基於@elliott-brossard 答案編輯)如果您有 2 個 arrays,但 1 個數組包含一個結構,您可以使用以下代碼將它們加在一起:
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
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