Calculating distances between two tables full of GEOGRAPHY points

Question

I'm using SQL Server.

I have two tables like this:

Table1:

Column1, Column2, Column3, GeoLoc
-----------------------------------
a        b        c        0xE61...

Table2:

Column1, Column2, Column3, GeoLoc 
-----------------------------------
a        b        c        0xE62...

I am looking to get an output table which will compare all of the points in both tables, and show me where table1 has a GeoLoc which is within X distance of GeoLoc in table2.

Does anyone know how to go about this? One table has around 800 rows, and the other has about 300,000 rows. I'm stumped as to even where to start...

Answer 1

Assuming your GeoLoc column is of the 'Geography' data type in SQL server, you should be able to use something like this:

select
  t1.*,
  t2.*,
  t1.GeoLoc.STDistance(t2.GeoLoc) as DistanceApart
from table1 t1
join table2 t2
on (t1.GeoLoc.STDistance(t2.GeoLoc) <= @distanceX)

with the 'DistanceApart' and 'distanceX' values being in meters