Which two statements are true about constraints? （）<br>A:The UNIQUE constraint does not permit a null value for the column.<br>B:A UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.<br>C:The PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.<br>D:The NOT NULL constraint ensures that null values are not permitted for the column.

Which two statements are true about constraints? （）
A:The UNIQUE constraint does not permit a null value for the column.
B:A UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.
C:The PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.
D:The NOT NULL constraint ensures that null values are not permitted for the column.

出自：Oracle认证

提示：
同一【IP】的非会员用户每天可免费获取10次答案

收藏本站【zk.995w.com】，下次访问不迷路

本站试题总数:【10245188】个 (题库试题定时更新)