Documentation Source Text

you can efficiently do inequality queries against the coordinate
ranges.  ^(To find all elements of the index that are contained within
the vicinity of Charlotte, North Carolina, one might do:
</p>

<blockquote><pre>
SELECT id FROM demo_index
 WHERE minX&gt;=-81.08 AND maxX&lt;=-80.58
   AND minY&gt;=35.00  AND maxY&lt;=35.44;
</pre></blockquote>)^

<p>
^The query above would very quickly locate the id of 1 even if the
R*Tree contained millions of entries.  The previous is an example
of a "contained-within" query.  The R*Tree also supports "overlapping"
queries.  ^(For example, to find all bounding boxes that overlap the
Charlotte area:
</p>

<blockquote><pre>
SELECT id FROM demo_index
 WHERE maxX&gt;=-81.08 AND minX&lt;=-80.58
   AND maxY&gt;=35.00  AND minY&lt;=35.44;
</pre></blockquote>)^

<p>
^(This second query would find both entry 1 (the SQLite.org office) which
is entirely contained within the query box and also
the 12th Congressional District which extends well outside the
query box but still overlaps the query box.)^
</p>

<p>
^Note that it is not necessary for all coordinates in an R*Tree index
to be constrained in order for the index search to be efficient.
^(One might, for example, want to query all objects that overlap with
the 35th parallel:
</p>

<blockquote><pre>
SELECT id FROM demo_index
 WHERE maxY&gt;=35.0  AND minY&lt;=35.0;
</pre></blockquote>)^

<p>
But, generally speaking, the more constraints that the R*Tree module
has to work with, and the smaller the bounding box, the faster the
results will come back.
</p>

the North Carolina 12th District, one may be to run a query like this:
</p>

<blockquote><pre>
SELECT objname FROM demo_data, demo_index
 WHERE demo_data.id=demo_index.id
   AND contained_in(demo_data.boundary, :boundary)
   AND minX&gt;=-81.0 AND maxX&lt;=-79.6
   AND minY&gt;=35.0 AND maxY&gt;=36.2;
</pre></blockquote>)^

<p>In the query above, one would presumably bind the binary BLOB 
description of the precise boundary of the 12th district to the
":boundary" parameter.</p>

<p>Notice how the query above works:  The R*Tree index runs in the outer