WITH ps AS ( 
    SELECT
        min(lat_n) x1, 
        min(long_w) y1,
        max(lat_n) x2, 
        max(long_w) y2 
    FROM station)
SELECT
    round(
        SQRT(
            POWER((x2-x1),2)
            +POWER((y2-y1),2)
            )
        ,4) euclidean_distance
FROM ps;