Re: Column as result of subtraction of two other columns?
От | Paul Thomas |
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Тема | Re: Column as result of subtraction of two other columns? |
Дата | |
Msg-id | 20040716161927.C20923@bacon обсуждение исходный текст |
Ответ на | Column as result of subtraction of two other columns? ("Mark Cave-Ayland" <m.cave-ayland@webbased.co.uk>) |
Список | pgsql-general |
On 16/07/2004 15:31 Mark Cave-Ayland wrote: > Hi everyone, > > I'm trying to calculate an output column which is the difference of two > other columns in the query output; the first column is an aggregate of > items in stock, while the second column is an aggregate of items which > have been used. The third column should should be the difference of the > two values so I can then output all three columns in a table. > > Unfortunately I can't get this to work at the moment :(. I've simplified > the query down to the following: > > dev=# select 1 as a, 2 as b, (b - a) as c; > ERROR: column "b" does not exist > dev=# > > Do I need to create some form of alias so the calculation can see the > other columns? I am using PostgreSQL 7.4.2 on Linux. I think you can use a sub-select (this works for me on 7.3.4): select a, b, (b - a) as c from (select .... as a, .... as b from mytable) as sub; HTH -- Paul Thomas +------------------------------+---------------------------------------------+ | Thomas Micro Systems Limited | Software Solutions for Business | | Computer Consultants | http://www.thomas-micro-systems-ltd.co.uk | +------------------------------+---------------------------------------------+
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