Re: Sorting by an arbitrary criterion

Поиск
Список
Период
Сортировка
От Grzegorz Jaśkiewicz
Тема Re: Sorting by an arbitrary criterion
Дата
Msg-id 2f4958ff0907091325v3f21dd96y7d8c0ae93513f052@mail.gmail.com
обсуждение исходный текст
Ответ на Re: Sorting by an arbitrary criterion  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-performance
2009/7/9 Tom Lane <tgl@sss.pgh.pa.us>:
> =?UTF-8?Q?Grzegorz_Ja=C5=9Bkiewicz?= <gryzman@gmail.com> writes:
>> On Thu, Jul 9, 2009 at 5:26 PM, Craig James<craig_james@emolecules.com> wrote:
>>> Suppose I have a large table with a small-cardinality CATEGORY column (say,
>>> categories 1..5).  I need to sort by an arbitrary (i.e. user-specified)
>>> mapping of CATEGORY, something like this:
>
>> you can create translation table, join it, and sort by its key.
>
> Much easier to
>        ORDER BY CASE category WHEN 'z' THEN 1 WHEN 'a' THEN 2 ... END
>
> Actually, consider putting the CASE into a function and doing
>        ORDER BY sort_order(category)

I suppose table is handy, when you have a lot of items as keys...



--
GJ

В списке pgsql-performance по дате отправления:

Предыдущее
От: "Hartman, Matthew"
Дата:
Сообщение: Re: Sorting by an arbitrary criterion
Следующее
От: "Albe Laurenz"
Дата:
Сообщение: Re: embedded sql regression from 8.2.4 to 8.3.7