多项选择题
A.It cannot be created without a package specification.
B.It cannot invoke subprograms defined in other packages.
C.It can contain only the subprograms defined in the package specification.
D.It can be changed and recompiled without making the package specification invalid.
单项选择题 Youworkinadatawarehouseenvironmentthatinvolvestheexecutionofcomplexqueries.ThecurrentcontentoftheSQLcacheholdstheidealworkloadforanalysis.Youwanttoanalyzeonlyfewmostresource-intensivestatements.Whatwouldbeyoursuggestiontoreceiverecommendationsontheefficientuseofindexesandmaterializedviewstoimprovequeryperformance？（）
多项选择题 WhichtwodatabaseoperationscanbeperformedattheMOUNTstageofdatabasestartup？（）
多项选择题 YourdatabaseisinNOARCHIVELOGmode.Afterwhichtwooperationsyoushouldtakethebackupofcontrolfile？（）