SQL案例：查找N公里内活跃商户

数据表 shopid, lot,lat,cot
查找N公里内平均cot大于W的商户
使用函数DIST(lot1,lat1,lot2,lat2)计算距离

SELECT shopid
FROM TABLE t1
GROUP BY shopid
HAVING W < AVG(
    SELECT cot
    FROM TABLE t2
    WHERE DIST(t1.lot,t1.lat,t2.lot,t2.lat) < N
)