Mysql - distance from a point

[dbrb2]

Hello,

I'm trying to get my head around MySQL GIS functionality. Can anyone tell me why the below query, lifted from a mysql example page, returns NULL whenever it is run? I am trying to use something similar to query a table based on distance from a point.

SELECT ROUND(GLength(
	LineStringFromWKB(
		LineString(
			AsBinary(GeomFromText('POINT(5571 3510)')),
			AsBinary(GeomFromText('POINT(0 3510)'))
			  )
			 )
	      )
      )
FROM dual;

Cheers,

Ben

 

[DonQuichote]

I don't know why, but the LineString function does not seem to like it when you feed it the output of AsBinary. So the following seems to work:

SELECT ROUND(GLength(
    LineStringFromWKB(
        LineString(
            GeomFromText('POINT(5571 3510)'),
            GeomFromText('POINT(0 3510)')
              )
             )
          )
      )
FROM dual;

Note: I don't know anything about the spatial functions. I just ran the query from the bottom (GeomFromText, then AsBinary, etc) and looked where it went wrong. One thing to remember is NULL propagation: whenever a value is NULL, most functions with that value as parameter also return NULL.

+++ Despite being wrong in every important aspect, that is a very good analogy +++
Hex (in Darwin's Watch)