为什么我不能限制我的排名（）？答案

【问题标题】：Why can't i limit my rank()?为什么我不能限制我的排名（）？
【发布时间】：2016-06-15 05:51:45
【问题描述】：

我正在尝试对排名功能进行限制，但我似乎无法使其发挥作用。我错过了什么？到目前为止，我在外部查询上使用了 WHERE/HAVING 函数：WHERE rank ，但我收到没有 Rank Column 的错误。

我一直在环顾四周，许多人也使用了别名。

    SELECT a.customer_name ,
       a.unit ,
       sum(a.price) - sum(b.price) AS "highest revenue" ,
       rank() over (partition BY a.unit
                    ORDER BY sum(a.price) - sum(b.price) DESC) AS "Rank"
FROM
  (SELECT customer_name ,
          unit ,
          price
   FROM table1
   WHERE booked BETWEEN '12/01/15' AND '12/31/15') a
JOIN
  (SELECT customer_name ,
          unit ,
          price
   FROM table1
   WHERE booked BETWEEN '11/01/15' AND '11/30/15') b ON a.unit = b.unit
GROUP BY a.customer_name,
         a.unit
ORDER BY a.unit,
         sum(a.price) - sum(b.price) DESC, rank() over (partition BY a.unit ORDER BY sum(a.price) - sum(b.price) DESC) DESC

【问题讨论】：

标签： postgresql greatest-n-per-group rank window-functions

【解决方案1】：

您不能在查询本身中使用别名，您应该将其全部包装在外部查询中：

SELECT customer_name, unit, "highest revenue", rank
FROM (
  SELECT a.customer_name, a.unit,
         sum(a.price - b.price) AS "highest revenue",
         rank() OVER (PARTITION BY a.unit
                      ORDER BY sum(a.price - b.price) DESC) AS rank
  FROM
    (SELECT customer_name, unit, price
     FROM table1
     WHERE booked BETWEEN '12/01/15' AND '12/31/15') a
  JOIN
    (SELECT customer_name, unit, price
     FROM table1
     WHERE booked BETWEEN '11/01/15' AND '11/30/15') b USING (unit)
  GROUP BY a.customer_name, a.unit) sub
ORDER BY unit, "highest revenue" DESC, rank DESC;

【讨论】：