A database backup is a restorable copy of database contents and structure kept separately from the live database. It is the safety net for schema changes that can erase existing data. section 10.2
Django migrations track table structure, not table contents. Removing a model field removes its database column and all data in it; there is no built-in undo. Make a backup before destructive changes. section 10.2
Changing the Promoter model
Replacing first_name and last_name with full_name and common_name requires deciding how existing rows will be converted. A backup preserves those rows if the migration or its assumptions go wrong. section 10.2
