On 23/01/2009 12:58 AM, Igor Tandetnik wrote:
> "Sergej Schwarz" <sergej.schw...@gmx.de> wrote in
> message news:20090122133954.74...@gmx.net
>> unfortunately, this does not work, the RTree documentation by SQLite
>> leads to misunderstanding of the concept... The query would results
>> in an empty set.
>>
>> //your query
>> select * from demo where x1>=3 and x2<=19 and y1>=2 and y2<=15;
>
> That's not at all similar to Dan's query. Try this:
>
> select * from demo where x1<=19 and x2>=3 and y1<=15 and y2>=2;
>
Some other comments:
(1) describe the shapes as rectangles rather than the too-general "polygons"
(2) consider
query1 UNION ... UNION query6
which at least saves the final step of removing duplicates, and may with
an ultra-smart query engine run faster
(3) consider that 6 queries of the form
SELECT yadda FROM blah WHERE condition[i]
can be replaced by one query of the form
SELECT yadda FROM blah WHERE (condition[1]) OR ... OR (condition[6])
(4) note that doing all the algebra to reduce that big expression would
not result in the same answer as Dan's ... Dan's formula includes the
case of a big rectangle that completely covers the window plus extra on
each of the four sides, but the OP's formula doesn't include that case.
By the way, we're all assuming a convention that x1 <= x2 and y1 <= y2,
aren't we?
HTH,
John
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