PostgreSQL distance between 2 points stored in table

Question

I have four fields lat1,lng1,lat2,lng2 and I would like to calculate the distance in km between them (rounded to 1 deciaml place).

For example table:

-----lat1-----|--- lng1 ----| ----lat2----|---lng2----|
 53.4603045   |  9,98243    |  53,4470272 | 9,9956593 |

I have tried:

   SELECT ST_Distance(POINT(lat1, lng1),POINT(lat2, lng2)) as distance FROM table

What do I have to change?

Answer 1

PostGIS is the answer.

I'll give it a go

Answer 2

If your postgres comes with plv8 extension (javascript), you can do something like this:

CREATE OR REPLACE FUNCTION distance_example(_la integer, _lb integer) RETURNS
real AS $$

  var locations = plv8.execute("SELECT * FROM location WHERE id IN ($1, $2)", [_la, _lb]);
  var x = locations[0].longitude - locations[1].longitude;
  var y = locations[0].latitude - locations[1].latitude;
  return Math.sqrt(x * x + y * y);
$$ LANGUAGE plv8 IMMUTABLE STRICT;

select distance_example();