Consider the relations :

R₁{Roll_no, Name, Grades} and

R₂ {Roll_no, Subject_ID, Grades}

Which of the following operations cannot be performed using the above relations ? 

The correct answer is Union.

Key Points

• Union operation in relational databases requires that the two relations have the same set of attributes (columns) and compatible domains (data types).
• In this case, we have two relations:
• R1 {Roll_no, Name, Grades}
• R2 {Roll_no, Subject_ID, Grades}
• These relations do not have the same set of attributes; R1 has (Roll_no, Name, Grades) and R2 has (Roll_no, Subject_ID, Grades).
• Because the attributes are not identical, we cannot perform the Union operation on these two relations.

Additional Information

• The Select operation can be performed to filter tuples based on a condition.
• The Join operation can be performed to combine tuples from R1 and R2 based on a common attribute (e.g., Roll_no).
• The Project operation can be performed to select specific attributes from a relation.