I want to store the values of latitude and longitude fetched from Google Maps GeoCoding API in a MySQL database. The values are in float format.
12.92
MySQL has special types for GIS applications.
Use the point type and see:
http://dev.mysql.com/doc/refman/5.0/en/spatial-extensions.html
For a general discussion see: http://dev.mysql.com/tech-resources/articles/4.1/gis-with-mysql.html
Some guys made a special UDF for computing distances between points on a sphere (i.e. earth)
See: http://www.lenzg.net/archives/220-New-UDF-for-MySQL-5.1-provides-GIS-functions-distance_sphere-and-distance_spheroid.html
Here's a howto: http://howto-use-mysql-spatial-ext.blogspot.com/2007/11/using-circular-area-selection.html