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