bigquery 通过时间戳和另一列连接两个表

Question

我有两张表如下：

TableA: host, timestamp, type
TableB: host, timestamp, type

我想按主机列和时间戳连接这两个表。它返回 null 因为通常时间戳之间有几秒钟的间隔，所以它们不匹配。所以我想根据主机和时间戳（仅限日期、小时和分钟）加入他们。 时间戳列是这样的：2020-11-06 23:33:03.448 UTC

我在下面创建了仅基于小时的查询，我想包括天、分钟（可能还有秒）。

  with tableA as (
      SELECT
      EXTRACT(HOUR from timestamp) as hour,
      ...
  ),
  tableB as (
      SELECT
      EXTRACT(HOUR from timestamp) as hour,
      ...
  )
  SELECT * 
  FROM tableA 
  JOIN tableB 
  USING(host,hour)

Answer 1

使用timestamp_trunc():

with tableA as (
      SELECT TIMESTAMP_TRUNC(timestamp, HOUR ) as hour,
             ...
     ),
     tableB as (
      SELECT TIMESTAMP_TRUNC(timestamp, HOUR ) as hour,
             ...
     )
SELECT * 
FROM tableA JOIN
     tableB 
     USING(host, hour);