Relational Rules

1. First Normal Form: Domains must be atomic. i.e multi-valued fields are not allowed. Example: The following relation is not in First Normal Form:

   

2. Access rows by content: There is no ordering to the rows of a table, i.e., we cannot access the first row or the fifth row or the last row etc.
3. Unique row rule: Since a relation was defined as a SET of tuples (rows), there should be no duplicates.
4. Entity integrity rule: Primary Key columns in a table CANNOT contain null values.