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.
Wouldn’t a NOT NULL constraint achieve this? Why is A correct?
Beacause we update an existing column, not adding a new one
Yes, NOT NULL constraint would achieve that. But you add it with Alter Table… Modify statement.
Alter table orders modify (odate not null);