Which type of backup in Azure SQL Database captures all changes since the last full backup?

The correct answer is a differential backup. A differential backup in Azure SQL Database specifically captures all changes made to the database since the last full backup was taken. This means that when you perform a differential backup, it records all the data modifications that have occurred after the last full backup, allowing for a more efficient recovery process.

Differential backups are beneficial because they reduce the amount of data that needs to be backed up at any given time compared to a full backup, which captures all data in the database. In this way, differential backups can help balance the need for data protection with the overhead that comes from making backups, as they require less storage space and can be quicker to perform and restore.

Transaction log backups, on the other hand, allow for point-in-time recovery by capturing all transactions that have occurred since the last backup, but they do not summarize changes since a full backup. Full backups capture the entire state of the database at a given moment without regard to earlier backups. Snapshot backups are typically used for creating a read-only copy of the database at a specific point in time and do not play a role in the incremental tracking of changes post-full backup.