Finding Locations Within A Specific Distance using PostGIS data within postgress

I am trying to find all locations within a one mile radius of a specified point. I have longitude and latitude data for each point,

multi polygon geometry (Example :

MULTIPOLYGON(((2147312.63139525 161631.130590368,2147298.94808962 164286.665686698,2147623.79332922 164287.328517173,2149920.27996486 164292.162599235,2149944.29540875 161654.921437815,2147312.63139525 161631.130590368)))

and the_geom data

Example:

0106000020DA08000001000000010300000001000000060000003F8FD150F86140417EF6720BF9BA03412C005B79F16140412A8C5353F50D0441D7CF8BE593624041929CCDA0FA0D044177E3D52310674041E5D3004D210E044134F4CF251C67404106CA1A5FB7BB03413F8FD150F86140417EF6720BF9BA0341

I'm just not sure of the best way to approach finding all distances within one mile.

Solution

To query geometries within a given radius you have to use ST_DWithin:

SELECT * FROM t
WHERE
  ST_DWithin(
    the_geom::geography,
    ST_MakePoint(longitude,latitude),1609.344); -- 1609.34 metres = 1 mile;

The geography cast enables you to search using metres as unit, which can be easily converted to miles.