title: Update same table with calculated distance
body: <p>This question is connected to <a href="https://gis.stackexchange.com/questions/162416/calculate-road-distance-between-gps-points">this:</a></p>
  
  <p>I can calculate distance with the new entries and insert into 4th column called distance. But now I need to make update query that uses ST_Distance to calculate progressive distance of existing GPS coordinates and store into distance column. Any idea how that can be achieved with my existing table design? </p>