DBS概念和组成Adatabase-managementsystem(DBMS)isacollectionofinterrelateddataandasetofprogramstoaccessthosedata.Thecollectionofdata,usuallyreferredtoasthedatabase,containsinformationrelevanttoanenterprise.DataAbstractionPhysicallevel.howthedataareactuallystoredLogicallevelwha