Examinethecode：CREATEROLEreadonlyIDENTIFIESUSINGapp.chk_readwrite；CREATEROLEreadwriteIDENTIFIEDUSINGapp.chk_readwrite；CREATEORREPLACePROCEDUREapp.chk_readwriteAUTHIDCURRENT_USERISipchkSTRING（30）；BEGINIFsys_context（‘USERENV’，’ISDBA’）=’TRUE’THENDBMS_SESSION.SET_ROLE‘READWRITE’）；ELSEDBMS_SESSION.SET_ROLE（‘READONLY’）；END；/WhichthreestatementscorrectlydescribetheSecureApplicationroledefinition？（）
A.Nouserorapplicationhastorememberorhideapassword.
B.ItpreventseveryoneexceptatrueDbasessionfromacquiringtheREADWRITErole.
C.app.chk_readwriteiscalledwheneverausertriestoaccessrowsprotectedbytheREADONLYorREADWRITElabel.
D.app.chk_readwriteiscalledbyusersorapplicationswhentheywanttoenabletheREADONLYor READWRITErole.
正确答案：参考A, B, D
