透视 BigQuery 中的重复字段

Question

我的架构看起来像这样：

userid:string
timestamp:integer
params:nested/repeated field with 2 fields
  - name:string (possible values: "a", "b","c")
  - value:string

我希望查询 return 以下内容：

userid, timestamp, a, b, c
123, 1447799796, foo, bar, xyz
233, 1447799900, bob, xxx, yyy
:
:

最简单的方法是什么？

Answer 1

大致如下：

SELECT 
  userid,
  timestamp,
  FIRST(name == "a", value, NULL) WITHIN RECORD a,
  FIRST(name == "b", value, NULL) WITHIN RECORD b,
  FIRST(name == "c", value, NULL) WITHIN RECORD c,
FROM t

Answer 2

当可能的值事先已知并且没有那么多可以手动编写时 SQL - 您可以使用以下内容：

SELECT 
  userid,
  ts,
  MAX(IF(params.name = "a", params.value, NULL)) WITHIN RECORD a,
  MAX(IF(params.name = "b", params.value, NULL)) WITHIN RECORD b,
  MAX(IF(params.name = "c", params.value, NULL)) WITHIN RECORD c
FROM yourTable

如果可能的值是 "unknown" 提前 and/or 动态来自运行运行，您可以使用下面的帮助程序 SQL 生成以上类型的 SQL。

SELECT 'select userid, ts, ' + 
   GROUP_CONCAT_UNQUOTED(
      'max(if(params.name = "' + STRING(params.name) + '", params.value, null)) 
       WITHIN RECORD as [' + STRING(params.name) + ']'
   ) 
   + ' from yourTable '
FROM (SELECT params.name FROM yourTable GROUP BY params.name)

透视 BigQuery 中的重复字段

Pivot Repeated fields in BigQuery

google-bigquery