SELECT on two UNIQUE columns

I am getting a doubt whether processing of the following query varies between ORACLE and INFORMIX embedded SQL ( c with sql)! exec sql select * from table1 where X = :x and Y = :y here both X and Y fields of the table are UNIQUE indices. So, if any of the fields have an equivalence, shouldn't the query return that ROW. other way is, both columns should match, only then is that row returned. Does Oracle function differenly! Any help is appreciated. Please post on the net, as it may be difficult reaching me directly. Thanks in advance. Ramesh Phatak