A.結(jié)構(gòu)化程度越來越高 B.共享性越來越好 C.獨(dú)立性越來越高 D.數(shù)據(jù)庫(kù)表越來越多
A.使用外鍵約束把Book_id列添加到Borrow表中 B.對(duì)Borrow_id列添加一個(gè)CHECK約束 C.為Book表增加一列來記錄書是否被借出 D.使用外鍵約束把Borrow_id列添加到Book表中
A.SELECT MIN(au_lname) FROM authors B.SELECT ADD(ytd_sales+1) FROM titles C.SELECT type,MAX(price) FROM titles GROUP BY type ORDER BY type D.SELECT COUNT(*) ,avg(price) FROM titles WHERE advance > $1000