sql 根据两点经纬度算出两点之间距离

select (sqrt(

    (

     ((121.544685-longitude)*PI()*12656*cos(((31.134857+latitude)/2)*PI()/180)/180)

     *

     ((121.544685-longitude)*PI()*12656*cos (((31.134857+latitude)/2)*PI()/180)/180)

    )

    +

    (

     ((31.134857-latitude)*PI()*12656/180)

     *

     ((31.134857-latitude)*PI()*12656/180)

    ))/2) as distance from tblschoolsite