Google BigQuery,我在使用 'unnest' 函数时丢失了空行

Google BigQuery, I lost null row when using 'unnest' function

#StandardSQL
WITH tableA AS (
SELECT ["T001", "T002", "T003"] AS T_id, [1, 5] AS L_id
UNION ALL
SELECT ["T008", "T009"] AS T_id, NULL AS L_id
)

SELECT * FROM tableA, UNNEST(L_id) AS unnest

当我执行这段代码时,我期望得到如下结果。

RowNumber  T-id            L-id  unnest
1          T001,T002,T003  1,5   1
2          T001,T002,T003  1,5   5
3          T004,T005       NULL  NULL

但我却得到了这个结果:

RowNumber  T-id            L-id  unnest
1          T001,T002,T003  1,5   1
2          T001,T002,T003  1,5   5

我丢了第三排。 然后,我看到了官方Google文档,其中说明如下:

UNNEST treats NULL as follows.
 ・NULL and empty ARRAY generate zero rows.
 ・An ARRAY containing NULL generates a row containing a NULL value.

但我不想丢失空行。

如何保留空行?

请告诉我解决方法...

不要使用 CROSS JOIN,而是使用 LEFT JOIN。这将为空数组 return 一行包含空值。您可能还对文档中的 working with arrays topic 感兴趣。

#StandardSQL
WITH tableA AS (
  SELECT ["T001", "T002", "T003"] AS T_id, [1, 5] AS L_id
  UNION ALL
  SELECT ["T008", "T009"] AS T_id, NULL AS L_id
)
SELECT * FROM tableA
LEFT JOIN UNNEST(L_id) AS value;