google-bigquery - 如何使用 BigQuery 模拟数据透视表？

Question

我需要按列组织查询结果，就像数据透视表一样。我怎样才能做到这一点？

Answer 1

2020 更新:fhoffa.x.pivot()

• https://towardsdatascience.com/easy-pivot-in-bigquery-one-step-5a1f13c6c710

<小时/>

使用条件语句将查询结果组织为行和列。在下面的示例中，对以值“Google”开头的大多数修订的维基百科文章的搜索结果被组织到列中，如果这些文章符合各种条件，则在其中显示修订计数。

SELECT
  page_title,
  /* Populate these columns as True or False, depending on the condition */
  IF(page_title CONTAINS 'search', INTEGER(total), 0) AS search,
  IF(page_title CONTAINS 'Earth' OR page_title CONTAINS 'Maps', INTEGER(total), 0) AS geo,
FROM
  /* Subselect to return top revised Wikipedia articles containing 'Google'
   * followed by additional text.
   */
  (SELECT
    TOP(title, 5) as page_title,
    COUNT(*) as total
   FROM
     [publicdata:samples.wikipedia]
   WHERE
     REGEXP_MATCH (title, r'^Google.+') AND wp_namespace = 0
  );

结果:

+---------------+--------+------+
|  page_title   | search | geo  |
+---------------+--------+------+
| Google search |   4261 |    0 |
| Google Earth  |      0 | 3874 |
| Google Chrome |      0 |    0 |
| Google Maps   |      0 | 2617 |
| Google bomb   |      0 |    0 |
+---------------+--------+------+

类似的示例，不使用子查询:

SELECT SensorType, DATE(DTimestamp), AVG(data) avg, 
FROM [data-sensing-lab:io_sensor_data.moscone_io13]
WHERE DATE(DTimestamp) IN ('2013-05-16', '2013-05-17')
GROUP BY 1, 2
ORDER BY 2, 3 DESC;

生成一个 3 列表:传感器类型、日期和平均数据。要“旋转”并将日期作为列:

SELECT
  SensorType,
  AVG(IF(DATE(DTimestamp) = '2013-05-16', data, null)) d16,
  AVG(IF(DATE(DTimestamp) = '2013-05-17', data, null)) d17
FROM [data-sensing-lab:io_sensor_data.moscone_io13]
GROUP BY 1
ORDER BY 2 DESC;