Module 7 - Normalization Flashcards
What is an independent entity?
An entity that can exist without a parent entity (Identifier is created from own attributes)
What is a dependent entity?
An entity that cannot exist without a parent entity (Identifier is consists of at least one attribute from parent entity)
What is normalization?
A method to create a consistent model by reducing redundancy and inconsistent data. Think of converting repetition into a value that spans across multiple rows in a table.
How can you tell if a table is in first normal form? (1NF)
If it does not contain attributes that have multiple values for a single instance of the entity (i.e. the instance of an entity does not span multiple rows)
What is second normal form?
No partial dependencies, repeating groups of attributes are reduced by breaking up a compound identifier to create two more entities.
What is third normal form?
No transient dependencies, attributes that depend on another attribute are removed and placed in a new entity with the parent attribute as the identifier.
What are three ways to validate an ERD?
Normalization
Design guidelines
Balancing ERDs with DFDs
What is partial dependency of an attribute?
When non-identifier attributes are dependent on only part of a compound identifier. This means you should split the compound identifier into two separate entities. Carry the dependent attribute over to the new entity.
What is a transitive dependency of an attribute?
When an attribute depends on a non-identifier attribute. This suggests that the dependent attribute should be in another entity.
What is third normal form (3NF) and how can we create it?
Third normal form is the result of partial and transitive dependencies being resolved. We resolve transitive dependencies by creating a new entity and transferring the transitive dependency. NOTE: The parent attribute will remain in the original and be an identifier for the new table.
