用 sql 查找距离最近的坐标点语句

select *
    from b t1
   where ((:x - t1.x1) (:x - t1.x1) + (:y - t1.y1) (:y - t1.y1)) =
         (select min((:x - t2.x1) (:x - t2.x1) + (:y - t2.y1) (:y - t2.y1)) as long
            from b t2);

:x , :y 为已知的a坐标，用的是勾股定律

select *,
(2 * 6378.137 *
ASIN(SQRT(POW(SIN(PI() * (111.86141967773438 - lat) / 360), 2) +
COS(PI() * 33.07078170776367 / 180) *
COS(lat * PI() / 180) *
POW(SIN(PI() * (33.07078170776367 - lng) / 360), 2)))) as juli
from area
order by juli asc limit 0, 20