RelationalDBDesign
RelationalDBDesign

Relational Constructs
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## Relational Database Notation

*Relational Database Notation* focuses on the physical modeling of a relational database.

The answer is that for some students relational notation will seem quite natural and for others it will take some getting used to. I will continue to represent entities using both styles, so if you prefer graphics to relational notation you will have a visual reference to make the explanations more understandable. All I ask is that you learn how to read relational notation. Doing so will allow you to study beyond this course and take advantage of resources that use*relational notation* to present their material.

DB Design for Mere Mortals

## Defining Normal Forms the Academic Way

The following are the precise academic definitions of Normal Forms.

The answer is that for some students relational notation will seem quite natural and for others it will take some getting used to. I will continue to represent entities using both styles, so if you prefer graphics to relational notation you will have a visual reference to make the explanations more understandable. All I ask is that you learn how to read relational notation. Doing so will allow you to study beyond this course and take advantage of resources that use

*Domain:*Determines the type of data values that are permitted for that attribute.*Primary key:*A field (or combination of fields) that uniquely identifies a record in a table.*Foreign key:*A field (or combination of fields) used to link tables; a corresponding primary key field occurs in the same database.*Data redundancy:*Duplication of data in a database.

DB Design for Mere Mortals

- 1st Normal Form (1NF):Eliminate repeating groups such that all records in all tables can be identified uniquely by a primary key in each table. In other words, all fields other than the primary key must depend on the primary key.
- 2nd Normal Form (2NF):All non-key values must be fully functionally dependent on the primary key. No partial dependencies are allowed. A partial dependency exists when a field is fully dependent on a part of a composite primary key.
- 3rd Normal Form (3NF):Eliminate transitive dependencies, meaning that a field is indirectly determined by the primary key. This is because the field is functionally dependent on another field, whereas the other field is dependent on the primary key.
- Boyce-Codd Normal Form (BCNF):Every determinant in a table is a candidate key. If there is only one candidate key, 3NF and BCNF are one and the same.
- 4th Normal Form (4NF):Eliminate multiple sets of multivalued dependencies.
- 5th Normal Form (5NF):Eliminate cyclic dependencies. 5NF is also known as Projection Normal Form (PJNF).
- Domain Key Normal Form (DKNF):DKNF is the ultimate application of normalization and is more a measurement of conceptual state, as opposed to a transformation process in itself.