Sql：SELECT行，时差很小

Question

我有一张桌子

event_id eventtypeid eventtimestamp

描述可以彼此接近的时间事件。我想找到事件对，其中eventtypes相等，时间戳之间的差异不是logner而不是3毫秒。

在sql中一般是否可以？我该如何制定这样的要求？

提前谢谢。

Answer 1

mget

Answer 2

这些查询通常最好用window function：

解决

SELECT eventtypeid, first, second, diff
FROM (
  SELECT eventtypeid, event_id AS first, lead(event_id) OVER w AS second,
         lead(eventtimestamp) OVER w - eventtimestamp AS diff
  FROM event_table
  WINDOW w AS (PARTITION BY eventtypeid ORDER BY eventtimestamp)
) sub
WHERE diff <= interval '3 milliseconds';

这通常比自我加入快得多。