1
Ordering of tuples: Theoretically based on set theory, tuples in a relation do not need to follow any specific order. Interchanging rows does not change the meaning of the relation.
2
Ordering of values within a tuple: Under the standard definition where an n-tuple is an ordered list of n values, the order of values is important (e.g., Roll_No, Name, Age). An alternative definition treats tuples as sets of attribute-value pairs, making order unnecessary, but the first definition is preferred for simplicity.
3
Atomic values and flat relational model: Each value in a tuple must be atomic (indivisible). Composite and multi-valued attributes are not allowed directly in RDBMS, leading to the flat relational model.
4
Null values: Nulls can represent values that are unknown, exist but are not available, or are not applicable to a specific tuple.
5
Interpretation of a relation: A relation schema acts as a declaration or assertion about entities or relationships, and each individual tuple represents a specific fact.