There are orphaned data (for example, the house was deleted, but apartments remain). How to put them into the new system?

Orphaned data refers to data that has lost its connection to parent entities (for example, apartments without a building). To correctly transfer such data to a new system, the following approaches can be used:

1. Create placeholders — for example, create a building record marked as "deleted" or "archived" to maintain the connection.
2. Mark data as orphaned — add a flag or status to indicate that these apartments are not linked to an existing building.
3. Transfer with history preservation — if possible, keep information that the building was deleted to retain context.
4. Discuss with the business — clarify how they want to see such data in the new system: delete, archive, or display with a warning.

Example: if a building is deleted but apartments remain, you can create a building record in the new system with a flag is_deleted = true and link the apartments to this building. This will help preserve data integrity and prevent information loss.