A.GROUP BY B.ORDER BY C.JOIN D.WHERE
A.int B.char(n) C.float D.numeric
A.數(shù)據(jù)共享 B.數(shù)據(jù)完整性 C.數(shù)據(jù)冗余度高 D.數(shù)據(jù)獨(dú)立性高