Google bigquery BigQuery-仅按分隔符拆分一次

有没有一种方法可以只被分隔符拆分一次？我的数据可能在多个索引处有分隔符。我希望能把一个场分解成两个独立的场

例如，当使用句点作为分隔符时，我希望字符串how.now.brown.cow拆分为两个字段：[how，now.brown.cow]

---

SPLIT（{field}，'delimiter'）[SAFE_OFFSET（0）]可以很好地获得第一部分，但是我的数据中可能有不相等的数组长度，因此连接其他索引时遇到问题。

下面是针对BigQuery标准SQL的

#standardSQL
WITH `project.dataset.table` AS (
  SELECT 'how.now.brown.cow' col UNION ALL
  SELECT 'how'
)
SELECT col, 
  SPLIT(col, '.')[OFFSET(0)] AS first_item,
  ( SELECT STRING_AGG(item, '.' ORDER BY OFFSET)
    FROM UNNEST(SPLIT(col, '.')) item WITH OFFSET 
    WHERE OFFSET > 0
  ) AS rest_of_items
FROM `project.dataset.table`  

有输出

Row col                 first_item  rest_of_items    
1   how.now.brown.cow   how         now.brown.cow    
2   how                 how         null     

注意：以上只是其中一种方法。看起来有很多方法可以达到相同的效果-例如

#standardSQL
WITH `project.dataset.table` AS (
  SELECT 'how.now.brown.cow' col UNION ALL
  SELECT 'how'
)
SELECT col, 
  REGEXP_EXTRACT(col, r'^([^.]*)\.?') AS first_item,
  REGEXP_EXTRACT(col, r'^[^.]*\.?(.*)$') AS rest_of_items
FROM `project.dataset.table`

有输出

Row col                 first_item  rest_of_items    
1   how.now.brown.cow   how         now.brown.cow    
2   how                 how      

---

下面是BigQuery标准SQL

#standardSQL
WITH `project.dataset.table` AS (
  SELECT 'how.now.brown.cow' col UNION ALL
  SELECT 'how'
)
SELECT col, 
  SPLIT(col, '.')[OFFSET(0)] AS first_item,
  ( SELECT STRING_AGG(item, '.' ORDER BY OFFSET)
    FROM UNNEST(SPLIT(col, '.')) item WITH OFFSET 
    WHERE OFFSET > 0
  ) AS rest_of_items
FROM `project.dataset.table`  

有输出

Row col                 first_item  rest_of_items    
1   how.now.brown.cow   how         now.brown.cow    
2   how                 how         null     

注意：以上只是其中一种方法。看起来有很多方法可以达到相同的效果-例如

#standardSQL
WITH `project.dataset.table` AS (
  SELECT 'how.now.brown.cow' col UNION ALL
  SELECT 'how'
)
SELECT col, 
  REGEXP_EXTRACT(col, r'^([^.]*)\.?') AS first_item,
  REGEXP_EXTRACT(col, r'^[^.]*\.?(.*)$') AS rest_of_items
FROM `project.dataset.table`

有输出

Row col                 first_item  rest_of_items    
1   how.now.brown.cow   how         now.brown.cow    
2   how                 how