（34）You created an ORDERS table with the following description:

name Null Type

ORD_ID NOT NULL NUMBER(2)

CUST_ID NOT NULL NUMBER(3)

ORD_DATE NOT NULL DATE

ORD_AMOUNT NOT NULL NUMBER (10,2)

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 have two constraints on one column.

B. You cannot add a primary key constraint if data exists in the column.

C. The primary key constraint can be created only at the time of table creation .

D. You can add the primary key constraint even if data exists, provided that there are no duplicate values.

答案：（D）

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OCP 1Z0-051-34

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