在我发的sql基础上改

如果你已经有一个基础的SQL查询，但想针对特定情况进行调整，可以提供具体的需求。例如，如果你想要考虑时间有效性（电子围栏只在某个时间段内有效），你可以添加额外的条件：

SELECT ef.id, ef.location 
FROM eFenceLocations ef
JOIN (
    SELECT 
        ST_ClosestPoint(eFenceLocations.location, ST_GeomFromText('用户当前位置')) AS closest_location,
        MIN(TIMESTAMPDIFF(SECOND, ef.start_time, NOW())) AS min_seconds_until_expire
    FROM eFenceLocations
    WHERE ef.end_time > NOW()
    GROUP BY ef.location
) as closest_with_time
ON ef.location = closest_with_time.closest_location
WHERE closest_with_time.min_seconds_until_expire <= 0 OR closest_with_time.min_seconds_until_expire >= ef.duration_in_seconds
ORDER BY distance ASC, min_seconds_until_expire ASC
LIMIT 1;

这里假设`start_time`和`end_time`分别是围栏的有效开始时间和结束时间，`duration_in_seconds`是从开始到结束的时间差。