Question

Which of the following SQL command can change the degree of the existing relation?

• A. DROP TABLE
• B. ALTER TABLE
• C. UPDATE…SET
• D. DELETE

Hint:

Degree means the number of columns. Only the command that changes table structure, ALTER TABLE, can add or drop a column.

Answer 1

The Correct Option is B

Step 1: Understand degree:
The degree of a relation is the number of columns (attributes) in the table.
To change the degree, a command must add a column, drop a column or change the structure of the table.

Step 2: Know which SQL group changes structure:
DDL (Data Definition Language) commands such as CREATE, ALTER and DROP change the structure of a table.
DML (Data Manipulation Language) commands such as INSERT, UPDATE and DELETE change only the data inside rows.

Step 3: Check option (A) DROP TABLE:
DROP TABLE removes the whole table from the database.
The table no longer exists, so it is not changed to a new degree. So (A) is wrong.

Step 4: Check option (B) ALTER TABLE:
ALTER TABLE can ADD a new column or DROP an existing column.
For example, ALTER TABLE INVENTORY ADD PRICE INT; raises the degree by 1.
So (B) is correct.

Step 5: Check options (C) and (D):
UPDATE...SET changes the values stored in existing rows. The number of columns stays the same.
DELETE removes rows, which changes the cardinality, not the degree.
So (C) and (D) are wrong.

Final Answer:
ALTER TABLE is the command that can change the degree of a relation. This is option (B).