weather-observation-station-20.sql

SET @rowindex := -1;

SELECT 
    ROUND(AVG(LAT_N), 4)
FROM (
    SELECT 
        @rowindex:=@rowindex + 1 AS rowindex,
        LAT_N
    FROM STATION
    ORDER BY LAT_N
) AS station
WHERE rowindex IN (FLOOR(@rowindex / 2), CEIL(@rowindex / 2));