Question

A relation in MySQL database consists of 2 tuples and 3 attributes. If 2 attributes are deleted and 4 tuples are added, what will be the cardinality of the relation?

• A. 4
• B. 5
• C. 6
• D. 7

Hint:

Cardinality means the number of rows. Deleting columns does not change it, and adding 4 rows to 2 rows gives 6.

Answer 1

The Correct Option is C

Step 1: Recall the terms:
Cardinality of a relation is the number of tuples (rows).
Degree of a relation is the number of attributes (columns).
The question asks for the cardinality, so only the rows matter.

Step 2: Write the starting values:
Tuples = 2 and attributes = 3.

Step 3: Apply the changes:
Deleting 2 attributes changes the degree from 3 to 1. It does not change the number of rows.
Adding 4 tuples changes the cardinality from 2 to 2 + 4 = 6.

Step 4: Check each option:
Option (A) 4 counts only the new rows.
Option (B) 5 comes from mixing the deleted attributes with the row count.
Option (C) 6 is 2 old rows + 4 new rows, which is correct.
Option (D) 7 adds one extra value without any reason.

Final Answer:
The cardinality of the relation is 6. This is option (C).