sql - 日期和按日期排序的PostgreSQL案例

我试图按特定日期筛选结果，但当我使用下面的代码时，我只得到CloseDate与当前日期匹配的结果。当CloseDate为空时，它不包括ResolvedDate的结果。
我试过：

(CASE WHEN (Closedate IS Null) then ResolvedDate, ELSE CloseDate END) AS FinalDate

但它接着说：

 "column FinalDate does not exist"

还有别的办法吗？
这是目前为止的代码。谢谢你的帮助。

SELECT
id,
(CASE WHEN (Closedate IS Null) then ResolvedDate, ELSE CloseDate END),
FROM cases
WHERE (EXTRACT (month FROM Closedate) = EXTRACT(month FROM current_date))
AND  ( EXTRACT(day from Closedate) = EXTRACT(day FROM current_date))

最佳答案

您应该使用COALESCE函数http://www.postgresql.org/docs/current/static/functions-conditional.html
试试这个：

SELECT
  id,
  COALESCE(CloseDate, ResolvedDate) AS FinalDate
FROM
  cases
WHERE
  (EXTRACT (month FROM COALESCE(CloseDate, ResolvedDate)) = EXTRACT(month FROM current_date)) AND
  (EXTRACT (day from COALESCE(CloseDate, ResolvedDate)) = EXTRACT(day FROM current_date))

应该可以。。。