sql - 选择第二个最新日期的条目

Question

所以通常情况下，如果我想获取此表中每种类型的最新版本:

type |    date
-----------------
  A  | 2008-07-06
  B  | 2014-08-02
  A  | 2009-12-27
  A  | 2004-03-01
  B  | 2008-10-17
  B  | 2015-01-01

我会这样做:

SELECT DISTINCT ON (type) type, date
FROM t
ORDER BY type, date DESC;

但是，如果我不想获取最新的，而是第二个最新的怎么办？所以:

type |    date
-----------------
  A  | 2008-07-06
  B  | 2014-08-02

Answer 1

嗯，正在看Grouped LIMIT in PostgreSQL: show the first N rows for each group? ，我想到了:

SELECT * FROM (
  SELECT type, date, ROW_NUMBER()
  OVER (PARTITION BY type ORDER BY date DESC) AS row FROM t
  ) tmp
WHERE tmp.row=2;