MYSQL Solution

SELECT ROUND(
    SQRT(
        (POWER((MAX(LAT_N) - MIN(LAT_N)),2)) + 
        (POWER((MAX(LONG_W) - MIN(LONG_W)),2))
        )
,4)
FROM STATION;

`

SQL Server Solution

SELECT 
    CAST(
       SQRT(POWER(MIN(LAT_N) - MAX(LAT_N), 2) + POWER(MIN(LONG_W) - MAX(LONG_W), 2)) 
       AS DECIMAL(15,4)
    ) AS [Euclidean Distance]
FROM STATION

After a lot of searching, I finally found the answer, because I had no idea that the Euclidean distance was the standard way to measure distance. Later, I got it and understood everything.

SET @min_lat_n = (SELECT MIN(lat_n) FROM station); set @min_long_w = (select min(long_w) from station); set @Max_lat_n = (select max(lat_n) from station); set @max_long_w = (select max(long_w) from station);

select round(sqrt(pow(@Max_lat_n - @min_lat_n, 2) + pow(@max_long_w - @min_long_w, 2)), 4) from station limit 1;

select round(sqrt(power(max(LAT_N)-min(LAT_N),2)+pow(max(LONG_W)-min(LONG_W),2)),4) from station; /* d≈ (Δx)^ 2+(Δy)^ 2

SELECT ROUND(SQRT(POWER(MAX(LAT_N)-MIN(LAT_N),2)+ POWER(MAX(LONG_W)-MIN(LONG_W),2)),4) FROM STATION