Consider the following relations X(S, Si, C) and Y(S, P, D) . Which of the…

Answer: Full outer join

Explanation: A full outer join returns all rows from both relations and fills NULL for attributes from the other relation when no matching tuple exists.

• Join key: the common attribute S is used to match tuples.

• Tuples present only in relation X will appear with NULLs for the attributes from relation Y (P, D).

• Tuples present only in relation Y will appear with NULLs for the attributes from relation X (Si, C).

• Tuples present in both relations will include values from both sides.

Resulting rows (S, Si, C, P, D):

1. S = J: Si = 1, C = M, P = S1, D = CA

2. S = B: Si = 2, C = N, P = P1, D = AB

3. S = R: Si = 3, C = H, P = D1, D = DC

4. S = T: Si = 4, C = G, P = NULL, D = NULL

5. S = A: Si = NULL, C = NULL, P = H1, D = MD

Why other joins do not satisfy the requirement: a join that returns only rows from the left relation misses tuples present only in the right; a join that returns only rows from the right misses tuples present only in the left; a natural/inner join returns only matching tuples and excludes non-matching ones.