联接表结果 Google BigQuery答案

【问题标题】：Join table results Google BigQuery联接表结果 Google BigQuery
【发布时间】：2017-04-21 02:36:29
【问题描述】：

我有两个 SQL 查询：

SELECT subreddit, count(subreddit) as count
FROM [fh-bigquery:reddit_comments.all] 
where author="***********" GROUP by subreddit ORDER BY count DESC;

与

SELECT subreddit, count(subreddit) as count
FROM [redditcollaborativefiltering:aggregate_comments.reddit_posts_all]
where author="***********" GROUP by subreddit ORDER BY count DESC;

我希望能够将这两个查询的结果合并为一个具有相同列的结果，但是，计数是彼此相加的。有什么简单的方法可以做到这一点？

【问题讨论】：

标签： mysql google-bigquery

【解决方案1】：

对于 BigQuery Legacy SQL（我看到您在示例中使用），您可以在下面使用：

#legacySQL
SELECT subredit, SUM(cnt) as cnt
FROM (SELECT subreddit, COUNT(subreddit) as cnt
       FROM [fh-bigquery:reddit_comments.all] 
       WHERE author = '***********'
       GROUP BY subreddit 
      ),
      (SELECT subreddit, COUNT(subreddit) as cnt
       FROM [redditcollaborativefiltering:aggregate_comments.reddit_posts_all] 
       WHERE author = '***********'
       GROUP by subreddit
      )
GROUP BY subreddit
ORDER BY cnt DESC

正如您在此处看到的 - Legacy SQL 中的逗号用作 UNION ALL

以上可以进一步简化

#legacySQL
SELECT subreddit, COUNT(subreddit) as cnt
FROM [fh-bigquery:reddit_comments.all],
  [redditcollaborativefiltering:aggregate_comments.reddit_posts_all]
WHERE author = '***********'
GROUP BY subreddit 
ORDER BY cnt DESC

您可以阅读有关 BigQuery 旧版 SQL 的 Comma as UNION ALL 的更多信息

【讨论】：

【解决方案2】：

您可以使用UNION ALL 和另一个聚合：

SELECT subredit, SUM(cnt) as cnt
FROM ((SELECT subreddit, count(subreddit) as cnt
       FROM [fh-bigquery:reddit_comments.all] 
       WHERE author = '***********'
       GROUP BY subreddit 
      ) UNION ALL
      (SELECT subreddit, count(subreddit) as cnt
       FROM [redditcollaborativefiltering:aggregate_comments.reddit_posts_all]
       WHERE author = '***********'
       GROUP by subreddit
      )
     ) sc
GROUP BY subreddit
ORDER BY cnt DESC;

【讨论】：