Q51.

Explain how indexing works internally.

Q52.

What is B-tree index?

Q53.

What is hash index?

Q54.

How does query optimizer work?

Q55.

What is cost-based optimization?

Q56.

What are different types of locks in SQL?

Q57.

Explain pessimistic vs optimistic locking.

Q58.

What is phantom read?

Q59.

What is dirty read?

Q60.

What is non-repeatable read?