Oracle IN&EXISTS的用法

SELECT * FROM (SELECT k001 FROM koxn GROUP BY k001) k,( SELECT Hacno FROM GJONM00P) g WHERE k.k001 = g.Hacno

SELECT * FROM (SELECT k001 FROM koxn GROUP BY k001) k WHERE EXISTS(SELECT 1 FROM GJONM00P g WHERE k.k001 = g.Hacno)

SELECT * FROM (SELECT k001 FROM koxn GROUP BY k001) k WHERE k001 IN(SELECT Hacno FROM GJONM00P g WHERE k.k001 = g.Hacno)