QUESTION NO: 61
You created an ORDERS table with the following description:
Exhibit:
You inserted some rows in the table. After some time, you want to alter the table by creating the
PRIMARY KEY constraint on the ORD_ID column.
Which statement is true in this scenario?
A. You cannot add a primary key constraint if data exists in the column
B. You can add the primary key constraint even if data exists, provided that there are no duplicate
values
C. The primary key constraint can be created only a the time of table creation
D. You cannot have two constraints on one column
Answer: B
答案解析：
参考：34：http://blog.csdn.net/rlhua/article/details/12921757
Explanation:
Oracle 1z0-051 Exam
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