A.連接數(shù)據(jù)庫 B.連接并選取數(shù)據(jù)庫 C.連接并打開數(shù)據(jù)庫 D.選取數(shù)據(jù)庫
A.defined() B.isdefin() C.isdefined() D.無
A.returns B.close C.return D.back