在 PostgreSQL 查询的窗口函数中使用别名

Question

我正在使用 PostgreSQL 版本 9.1 并查看 Postgres 文档，我知道可以执行以下操作：

SELECT salary, sum(salary) OVER (ORDER BY salary) FROM empsalary;

这适用于我的查询。

现在我需要能够在 OVER (ORDER BY ...) 中指定别名而不是列名？

我已经尝试过：

编辑：我之前忘记将rank()添加到此查询中：

SELECT salary, <complex expression> as result, rank() OVER (ORDER BY result) FROM empsalary;

并且我收到一条错误消息，指出column“result”确实不存在。

是否可以在此处指定别名而不是列名？我错过了一些特殊的语法吗？

编辑：

我正在使用 Hibernate，并使用一些用于窗口函数的本机 SQL。生成并执行的完整 SQL 如下：

select 
       rank() OVER (ORDER BY deltahdlcOverruns DESC) as rank, 

       this_.deviceNo as y1_, 

       (SELECT _dev_.hdlcOverruns FROM abstractperformancestatistic _abs_ 
        INNER JOIN enddevicestatistic _dev_ ON _dev_.id = _abs_.id 
        INNER JOIN linkstatistic _link_ ON _link_.id = _dev_.linkStatistic_id 
        INNER JOIN iptstatistic _ipt_ ON _ipt_.id = _link_.iptStat_id 
        WHERE this_.deviceNo=_dev_.deviceNo AND _abs_.dateTime <= '3910-06-07 00:00:00.0'
        ORDER BY _abs_.dateTime DESC LIMIT 1
       ) 
       - 
       (SELECT _dev_.hdlcOverruns FROM abstractperformancestatistic _abs_ 
        INNER JOIN enddevicestatistic _dev_ ON _dev_.id = _abs_.id 
        INNER JOIN linkstatistic _link_ ON _link_.id = _dev_.linkStatistic_id 
        INNER JOIN iptstatistic _ipt_ ON _ipt_.id = _link_.iptStat_id 
        WHERE this_.deviceNo=_dev_.deviceNo AND _abs_.dateTime >= '3870-06-01 00:00:00.0' 
        ORDER BY _abs_.dateTime LIMIT 1
       ) 
       AS deltahdlcOverruns from EndDeviceStatistic this_ 

       inner join AbstractPerformanceStatistic this_1_ on this_.id=this_1_.id 
       inner join AbstractEntity this_2_ on this_.id=this_2_.id 
       left outer join RawEndDeviceStatistic this_3_ on this_.id=this_3_.id 
       left outer join LinkStatistic l2_ on this_.linkStatistic_id=l2_.id 
       left outer join AbstractPerformanceStatistic l2_1_ on l2_.id=l2_1_.id 
       left outer join AbstractEntity l2_2_ on l2_.id=l2_2_.id 
       left outer join RawLinkStatistic l2_3_ on l2_.id=l2_3_.id 
       left outer join IPTStatistic i1_ on l2_.iptStat_id=i1_.id 
       left outer join AbstractPerformanceStatistic i1_1_ on i1_.id=i1_1_.id 
       left outer join AbstractEntity i1_2_ on i1_.id=i1_2_.id 
       left outer join RawIPTStatistic i1_3_ on i1_.id=i1_3_.id 

       where this_1_.dateTime between ? and ? 

       group by this_.deviceNo limit ?

Answer 1

将别名放在 OVER 子句后面：

SELECT salary
     , sum(salary) OVER (ORDER BY salary) AS my_alias
FROM   empsalary;

问题更新后编辑

您不能在 SELECT< 的同一级别引用列别名（“输出列”） /代码>。为此，您需要一个子选择或 CTE 。就像：

SELECT id, result, rank() OVER (ORDER BY result) AS rnk
FROM  (
    SELECT id, <complex expression> AS result
    FROM   tbl
    WHERE  <some condition>
    GROUP  BY id
    ) sub;

对于您的查询：

SELECT rank() OVER (ORDER BY deltahdlcOverruns) AS rnk
     , y1_
     , deltahdlcOverruns
FROM  (
    SELECT this_.deviceNo as y1_
        ,  (SELECT _dev_.hdlcOverruns FROM abstractperformancestatistic _abs_ 
            JOIN   enddevicestatistic _dev_ USING (id)
            JOIN   linkstatistic _link_ ON _link_.id = _dev_.linkStatistic_id 
            JOIN   iptstatistic _ipt_ ON _ipt_.id = _link_.iptStat_id 
            WHERE  this_.deviceNo=_dev_.deviceNo
            AND    _abs_.dateTime <= '3910-06-07 00:00:00.0'
            ORDER  BY _abs_.dateTime DESC
            LIMIT  1
           ) 
           - 
           (SELECT _dev_.hdlcOverruns FROM abstractperformancestatistic _abs_ 
            JOIN   enddevicestatistic _dev_ USING (id)
            JOIN   linkstatistic _link_ ON _link_.id = _dev_.linkStatistic_id 
            JOIN   iptstatistic _ipt_ ON _ipt_.id = _link_.iptStat_id 
            WHERE  this_.deviceNo=_dev_.deviceNo
            AND    _abs_.dateTime >= '3870-06-01 00:00:00.0' 
            ORDER  BY _abs_.dateTime
            LIMIT  1
           ) AS deltahdlcOverruns
    FROM   EndDeviceStatistic this_ 
    JOIN   AbstractPerformanceStatistic this_1_ USING (id)
    JOIN   AbstractEntity this_2_ USING (id)
    LEFT   JOIN RawEndDeviceStatistic this_3_ USING (id)
    LEFT   JOIN LinkStatistic l2_ ON this_.linkStatistic_id = l2_.id 
    LEFT   JOIN AbstractPerformanceStatistic l2_1_ ON l2_.id = l2_1_.id 
    LEFT   JOIN AbstractEntity l2_2_ ON l2_.id = l2_2_.id 
    LEFT   JOIN RawLinkStatistic l2_3_ ON l2_.id = l2_3_.id 
    LEFT   JOIN IPTStatistic i1_ ON l2_.iptStat_id = i1_.id 
    LEFT   JOIN AbstractPerformanceStatistic i1_1_ ON i1_.id = i1_1_.id 
    LEFT   JOIN AbstractEntity i1_2_ ON i1_.id = i1_2_.id 
    LEFT   JOIN RawIPTStatistic i1_3_ ON i1_.id = i1_3_.id 
    WHERE  this_1_.dateTime between ? and ? 
    GROUP  BY this_.deviceNo
    LIMIT  ?
) x;

我做了一些额外的语法简化。

Answer 2

将窗口包装在周围的查询中：

SELECT salary, result OVER (ORDER BY result)
FROM (SELECT salary, (...expression...) AS result
      FROM empsalary
     ) x