Question

我正在尝试将所有comment个表（每月的评论碎片）加入posts表。有没有办法让我在内部联接之前执行联合？有关union all运算符的详细信息，请参阅文档here。我的查询只有一个评论表如下：

SELECT c.score, c.body, c.link_id, c.parent_id, p.created_utc, c.created_utc
FROM [fh-bigquery:reddit_comments.2016_01] AS c
INNER JOIN [fh-bigquery:reddit_posts.full_corpus_201512] AS p
ON c.parent_id = p.name
WHERE SUBSTR(c.parent_id, 1, 2) = 't3'
ORDER BY c.score DESC
LIMIT 10

Answer 1

替换

FROM [fh-bigquery:reddit_comments.2016_01] AS c

带

FROM (
  SELECT score, body, link_id, parent_id, created_utc 
  FROM (TABLE_QUERY([fh-bigquery:reddit_comments], 
                    'REGEXP_MATCH(table_id, r"\d{4}_\d{2}")')) 
) AS c

希望，这会给你一个想法详情请见Table wildcard functions和Regular expression functions

Answer 2

正如Mikhail Berlyant在他的回答中指出的那样，修改查询就完成了我所需要的。

SELECT c.score, c.body, c.link_id, c.parent_id, p.created_utc, c.created_utc, (c.created_utc - p.created_utc) AS time_diff
FROM (
  SELECT * 
  FROM 
    [fh-bigquery:reddit_comments.2015_11],
    [fh-bigquery:reddit_comments.2015_12],
    [fh-bigquery:reddit_comments.2016_01],
) AS c
INNER JOIN [fh-bigquery:reddit_posts.full_corpus_201512] AS p
ON c.parent_id = p.name
WHERE SUBSTR(c.parent_id, 1, 2) = 't3'
ORDER BY c.score DESC
LIMIT 100

如何使用BigQuery的联合所有内部联接？

2 个答案: