What types of locks exist at the database level?

Databases have different types of locks that ensure data integrity and consistency during concurrent access. The main types of locks:

• Row-level locks — lock individual records, minimizing contention.
• Table-level locks — lock the entire table, providing coarser control.
• Page-level locks — lock data pages, an intermediate level.

By lock type:

• Shared lock (S-lock) — allows reading but blocks writing.
• Exclusive lock (X-lock) — blocks both reading and writing.

There are also:

• Intent locks — used to indicate the intention to acquire a coarser lock.
• Deadlock — a situation where transactions mutually block each other.

Different DBMSs may have different mechanisms and names, but conceptually, locks serve to manage concurrent access and maintain transaction isolation.