OCP 1Z0 052 165

165. You have an ORDERS table with the following structure:

Name Null? Type

------------------------- -------- -------------------------

OID NUMBER(6)

ODATE DATE

CCODE NUMBER(6)

OAMT NUMBER(10,2)

The table has data in the ODATE column for all rows. Many orders are placed in a single day. You need to

ensure that the ODATE column must contain data for every order in future. Which method would serve

the purpose?

A.Modify the column using the ALTER TABLE...MODIFY command.

B.Add a UNIQUE constraint to the column using the ALTER TABLE...ADD CONSTRAINT command.

C.Add a NOT NULL constraint to the column using the ALTER TABLE...ADD CONSTRAINT command.

D.Add a PRIMARY KEY constraint to the column using the ALTER TABLE...ADD CONSTRAINT

command.

Answer: A

SQL> alter table orders modify odate not null;

Table altered.

SQL> alter table orders modify odate null;

Table altered.

SQL> alter table orders add constraints ch_odate check(odate is not null);

Table altered.

我认为按需求过说，D也对