gis - See if lat / long falls within a polygon using mysql

Question

I have the created the table below

CREATE TABLE geom (g GEOMETRY);

and have inserted many rows, example below:

INSERT INTO geom (g)
VALUES(PolygonFromText('POLYGON((
9.190586853 45.464518970,
9.190602686 45.463993916,
9.191572471 45.464001929,
9.191613325 45.463884676,
9.192136130 45.463880767,
9.192111509 45.464095594,
9.192427961 45.464117804,
9.192417811 45.464112862,
9.192509035 45.464225851,
9.192493139 45.464371079,
9.192448471 45.464439002,
9.192387444 45.464477861,
9.192051402 45.464483037,
9.192012814 45.464643592,
9.191640825 45.464647090,
9.191622331 45.464506215,
9.190586853 45.464518970))')
);

Now I want to search all the data and return the entries where a lat / long I have falls withn any of the polygons.

How can this be done using mysql? or is anyone aware of any links that will point me in the right direction?

Answer 1

MySQL as of v5.1 only supports operations on the minimum bounding rectangles (MBR). While there is a "Contains" function which would do what you need, it is not fully implemented and falls back to using MBRContains

From the relevant manual page

Currently, MySQL does not implement these functions according to the specification. Those that are implemented return the same result as the corresponding MBR-based functions. This includes functions in the following list other than Distance() and Related().

These functions may be implemented in future releases with full support for spatial analysis, not just MBR-based support.

What you could do is let MySQL give you an approximate result based on MBR, and then post process it to perform a more accurate test. Alternatively, switch to PostGIS!

(Update May 2012 - thanks Mike Toews)

MySQL 5.6.1+ offers functions which use object shapes rather than MBR

MySQL originally implemented these functions such that they used object bounding rectangles and returned the same result as the corresponding MBR-based functions. As of MySQL 5.6.1, corresponding versions are available that use precise object shapes. These versions are named with an ST_ prefix. For example, Contains() uses object bounding rectangles, whereas ST_Contains() uses object shapes.