Data Mapper, Repository and Unit of Work patterns

I'm learning about the following patterns

• Data Mapper
• Repository
• Unit of Work

I think I understand each of them but I can't answer these questions

• are they always used to together?
• which pattern uses the others?
• which pattern is known by the Domain Model?
• what CRUD operations are handled by each of them?
• who owns the database code (i.e. SQL)?

Thanks.