Summary of Fundamental Database Principles | VantageCloud Lake - Summary of Fundamental Database Principles - Teradata Vantage

Teradata® VantageCloud Lake
Deployment
VantageCloud
Edition
Lake
Product
Teradata Vantage
Published
January 2023
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en-US
ft:lastEdition
2024-12-11
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phg1621910019905

The following table summarizes the rules presented in this section.

Principle Definition
Entity integrity rule The attributes of the primary key of a relation cannot be null.

This rule applies to any candidate key of a relation, not only to the candidate key chosen to be the primary key.

This rule is explicitly intended to apply to base relations only and not virtual relations (views), thereby violating the principle of interchangeability.
Referential integrity rule
Referential integrity is supported only on the Block File System on the primary cluster, not on the Object File System.
 There cannot be any unmatched foreign key values.

Restated more formally, assume a primary key value PK in relvar T 1 and a candidate key value FK in relvar T 2 that references it.

The Referential Integrity Rule states that if FK references PK, then PK must exist.

The Referential Integrity Rule permits the attributes of FK to be wholly or partly null, which violates the Entity Integrity Rule because FK must reference a candidate key in T1, and no attribute of a candidate key can be null.
Information principle A relational database contains nothing but relation variables. That is, the information content of a relational database at any given instant is represented as explicit values (nulls are not values) in attribute positions in tuples in relations.
Closed world assumption A statement that is true is also known to be true. Conversely, what is not known to be true is false.
Principle of interchangeability No arbitrary or unnecessary distinctions are made between base relations (base tables) and virtual relations (views).
Principles of normalization
  • A relation variable that is not in 5NF must be decomposed into a set of 5NF projections.
  • The decomposition must be non-loss.
  • The decomposition must preserve dependencies.
  • Every projection on the non-5NF relvar must be required to reconstruct the original relvar from those projections.
  • The decomposition stops when its relation variables are in 5NF (or, situation permitting, 6NF).
Principle of orthogonal design No two relations in a relational database are defined to represent the same facts.
Assignment principle After value x is assigned to variable V, the comparison V=x must evaluate to TRUE.
Golden rule No update operation can ever cause any database constraint to evaluate to FALSE.

That is, no statement can leave any relvar with a value that violates its relvar predicate.

See Relations, Relation Values, and Relation Variables.
Principle of the identity of indiscernibles Every entity has its own identity.

Let E 1 and E 2 be any two entities. If there is no way to distinguish between E 1 and E 2, then E 1 and E 2 are identical: one thing, not two.