http://www.gurubee.net/article/53246 <--- 확인해보세요
SELECT pi_x, pi_y , SQRT( POWER(( 37.4917910 - pi_x) * 110979.309, 2) + POWER((127.4875970 - pi_y) * 88907.949, 2) ) z FROM t , (SELECT 37.4917910 v_x -- 기준좌표-위도 , 127.4875970 v_y -- 기준좌표-경도 , 110979.309 r_x -- 위도-거리 환산계수 , 88907.949 r_y -- 경도-거리 환산계수 , 500.000 v_z -- 검색반경 FROM dual ) WHERE SQRT( POWER((v_x - pi_x) * r_x, 2) + POWER((v_y - pi_y) * r_y, 2) ) <= v_z AND pi_x BETWEEN v_x - v_z / r_x AND v_x + v_z / r_x AND pi_y BETWEEN v_y - v_z / r_y AND v_y + v_z / r_y ORDER BY z ;