写法1：错误

select id,name,round(st_distance_sphere(point(138.12,32.12),point(`long`,`lat`))/1000, 2) distance from `shops` where distance>1000

写法2：正确

select id,name,round(st_distance_sphere(point(138.12,32.12),point(`long`,`lat`))/1000, 2) distance from `shops` where round(st_distance_sphere(point(138.12,32.12),point(`long`,`lat`))/1000, 2)>1000

写法3：正确

select id,name,round(st_distance_sphere(point(138.1231231,32.12312),point(`long`,`lat`))/1000, 2) distance from `shops` having distance>1000

问题

为什么 round(st_distance_sphere(point(138.12,32.12),point(long,lat))/1000, 2)要用having？