Using an alias in a window function in a query in PostgreSQL

Question

I am using PostgreSQL version 9.1 and looking at the Postgres docs, I know it is possible to do the following:

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

and this works for my queries.

Now I need to be able to specify an alias instead of a column name in the OVER (ORDER BY ...) ?

I have tried this:

EDIT: I previously forgot to add the rank() to this query:

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

and I am getting an error saying that column "result" does not exist.

Is it possible to specify an alias instead of a column name here? Am I missing some special syntax?

EDIT:

I am using Hibernate, with some native SQL for the window function. The full SQL that is generated and executed is below:

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

Place the alias behind the OVER clause:

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

Edit after question update

You cannot reference a column alias (an "output column") at the same level of a SELECT. You need a subselect or a CTE for this. Like:

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;

For your query:

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;

I made a few additional syntax simplifications.