What does each change in a database represent?

Each change in a database represents a transaction. In database management, a transaction refers to any single unit of work that includes one or more operations—such as updates, inserts, or deletions—that are performed as a single logical action. Transactions are crucial because they ensure that the database maintains integrity and consistency.

When a transaction is performed, it can be committed, meaning that all changes made during that transaction are saved to the database, or it can be rolled back, which undoes all changes, maintaining the data in its prior state. This mechanism is vital for error recovery and maintaining data integrity during concurrent operations.

The other choices pertain to specific actions or concepts within database operations but do not encompass the entirety of what changes represent. An update command is just one form of operation within a transaction, while a deleted entry is the result of a specific action rather than the transaction itself. Data redundancy refers to unnecessary duplication of data, which is an issue to be managed rather than a representation of changes in the database.