GATE Databases 2

Question 1

Which normal form eliminates transitive dependencies in a relation?

Accepted Answer

3NF

Answer

3NF removes transitive dependencies where a non-key attribute depends on another non-key attribute.

Question 2

In SQL, which isolation level prevents dirty reads but allows non-repeatable reads?

Accepted Answer

READ COMMITTED

Answer

READ COMMITTED ensures a transaction only reads committed data, preventing dirty reads but not non-repeatable reads.

Question 3

What is the result of a natural join between R(A,B,C) and S(B,C,D)?

Accepted Answer

A relation with attributes A,B,C,D joined on B and C

Answer

Natural join automatically joins on all common attributes (B and C) and produces a result with no duplicate columns.

Question 4

In the context of B+ trees, what is the minimum number of keys in a non-root node of order m?

Accepted Answer

⌈m/2⌉ - 1

Answer

A non-root node in a B+ tree of order m must have at least ⌈m/2⌉ - 1 keys to maintain the fill-factor invariant.

Question 5

Which relational algebra operation is equivalent to the SQL HAVING clause?

Accepted Answer

Selection (σ) applied after aggregation

Answer

HAVING filters groups after aggregation, equivalent to applying selection on the result of a group-by aggregation in relational algebra.

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