Data Model

A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to properties of the real world. For instance, a data model may specify that a data element representing a car comprise a number of other elements which in turn represent the color, size and owner of the car.

Types

A database model is a specification describing how a database is structured and used. Several such models have been suggested.

Flat Model

Hierarchical Model

Network Model

Relational Model

The purpose of the relational model is to provide a declarative method for specifying data and queries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for answering queries.

Database Normalization

Normalization involves decomposing a table into less redundant (and smaller) tables without losing information; defining foreign keys in the old table referencing the primary keys of the new ones. The objective is to isolate data so that additions, deletions, and modifications of an attribute can be made in just one table and then propagated through the rest of the database using the defined foreign keys.

1NF - First Normal Form

2NF - Second Normal Form

3NF - Third Normal Form

EKNF - Elementary Key Normal Form

BCNF - Boyce-Codd Normal Form

4NF - Fourth Normal Form

ETNF - Essential Tuple Normal Form

5NF - Fifth Normal Form

6NF - Sixth Normal Form

DKNF - Domain/Key Normal Form

UF -Unnormalized Form

Object-Oriented Model

Star Schema

Snowflake Schema

The snowflake schema is similar to the star schema. However, in the snowflake schema, dimensions are normalized into multiple related tables, whereas the star schema's dimensions are denormalized with each dimension represented by a single table. A complex snowflake shape emerges when the dimensions of a snowflake schema are elaborate, having multiple levels of relationships, and the child tables have multiple parent tables ("forks in the road").

Key-Value Pair

By far, the simplest of the NoSQL (not-only-SQL) databases in a big data environment are those employing the key-value pair (KVP) model. KVP databases do not require a schema (like RDBMSs) and offer great flexibility and scalability.