- Transactions are the basic unit of concurrency control
- Four characteristics of transactions:
- Atomicity: All operations contained in a transaction either all succeed or all fail and roll back.
- Consistency: Consistency is maintained before and after the transaction execution.
- Isolation: Multiple transactions concurrently operate on the same table in the database and are isolated from each other.
- Persistence: After a transaction commits successfully, changes to data are permanent.
- Three paradigms for database design:
- First normal form: atomicity of fields, in which all fields in a table are non-separable attribute values.
- Second normal form: All fields except the primary key are completely dependent on the primary key, not partially.
- Third normal form: all fields except the primary key depend directly on the primary key and cannot be transitive dependencies.