Re: join table with itself? - Mailing list pgsql-sql

From T E Schmitz
Subject Re: join table with itself?
Date
Msg-id 45F99675.5050801@numerixtechnology.de
Whole thread Raw
In response to Re: join table with itself?  ("William Leite Araújo" <william.bh@gmail.com>)
List pgsql-sql
William Leite Araújo wrote:
> On 15/03/07, *T E Schmitz* <mailreg@numerixtechnology.de 
> <mailto:mailreg@numerixtechnology.de>> wrote:
> (...)
>  
>    Try join the tables.
> 
>     SELECT  present.day, present.low, (MIN(future.day)-present.day) as
> 
>     days2fall FROM history AS present JOIN history AS future ON (
>     present.day < future.day AND
>          future.low <= present.low )
>     GROUP BY present.day,present.low
>     ORDER BY days2fall DESC

That produces the same result as my previous example but maybe the join 
is more efficient, Thank you for the suggestion.

However, I am still stuck as to how to retrieve HIGHEST. The result set 
produced by the above query only contains those tuples whose LOW is 
lower than present.LOW.

For HIGHEST, I need to look at the rows between present.day and DAYS2FALL:

something like

SELECT MAX (high) from history WHERE day >= present.day AND day < 
(present.day + days2fall)

-


Regards,

Tarlika Elisabeth Schmitz


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