Can you explain what is meant by consistency in the context of databases?

Consistency in the context of databases is a property that guarantees that after a transaction is executed, the database remains in a correct state, satisfying all specified constraints and rules (such as integrity constraints, uniqueness, foreign keys).

If a transaction violates these rules, it should be rolled back to prevent the database from becoming inconsistent. Thus, consistency is part of the ACID model, which ensures data correctness after modification operations.

Example: if there is a rule in the database that the sum in accounts cannot be negative, then a transaction that results in a negative balance should be rejected to maintain consistency.