String Aggregtion to create pivot columns in Big Query

问题

I am trying to implement this exact solution linked below, but it seems GROUP_CONCAT_UNQUOTED is no longer a valid BQ function. Is there a solution to this that works in 2020?

p.s. I would have just commented on the original post, but apparently my reputation isn't high enough yet...

Transpose rows into columns in BigQuery (Pivot implementation)

回答1:

Below example is for BigQuery Standard SQL

Assume you have data as below

#standardSQL
WITH `project.dataset.table` AS (
  SELECT 1 id, 'channel_title' key, 'Mahendra Guru' value UNION ALL
  SELECT 1, 'youtube_id', 'ugEGMG4-MdA' UNION ALL
  SELECT 1, 'channel_id', 'UCiDKcjKocimAO1tV' UNION ALL
  SELECT 1, 'examId', '72975611-4a5e-11e5' UNION ALL
  SELECT 1, 'postId', '1189e340-b08f' UNION ALL

  SELECT 2, 'channel_title', 'Ab Live' UNION ALL
  SELECT 2, 'youtube_id', '3TNbtTwLY0U' UNION ALL
  SELECT 2, 'channel_id', 'UCODeKM_D6JLf8jJt' UNION ALL
  SELECT 2, 'examId', '72975611-4a5e-11e5' UNION ALL
  SELECT 2, 'postId', '0c3e6590-afeb' 
)

to get those keys pivoted - you can use below query

#standardSQL
SELECT id, 
  MAX(IF(key = "channel_id", value, NULL)) AS `channel_id`,
  MAX(IF(key = "channel_title", value, NULL)) AS `channel_title`,
  MAX(IF(key = "examId", value, NULL)) AS `examId`,
  MAX(IF(key = "postId", value, NULL)) AS `postId`,
  MAX(IF(key = "youtube_id", value, NULL)) AS `youtube_id` 
FROM `project.dataset.table` 
GROUP BY id

with result

Row id  channel_id          channel_title   examId              postId          youtube_id   
1   1   UCiDKcjKocimAO1tV   Mahendra Guru   72975611-4a5e-11e5  1189e340-b08f   ugEGMG4-MdA  
2   2   UCODeKM_D6JLf8jJt   Ab Live         72975611-4a5e-11e5  0c3e6590-afeb   3TNbtTwLY0U

to make your life simpler and not to type all those line for each and every key - you can instead generate the whole SQL text using below query

#standardSQL
SELECT 'SELECT id, ' || 
   STRING_AGG(
      'MAX(IF(key = "' || key || '", value, NULL)) as `' || key || '`'
   ) 
   || ' FROM `project.dataset.table` GROUP BY id ORDER BY id'
FROM (
  SELECT key 
  FROM `project.dataset.table`
  GROUP BY key
  ORDER BY key
)

Note: the post you mentioned in your question was given in 2016 and for Legacy SQL

来源：https://stackoverflow.com/questions/61528721/string-aggregtion-to-create-pivot-columns-in-big-query

标签

google-bigquery

pivot

string-function