Types of Databases /Database Models

There are several common types of databases; each type of database has its own data model (how the data is structured). They include;  Flat Model, Hierarchical Model, Network Model, Relational Model ,Dimensional Model and Object Oriented Model.

1. Flat Model
   • The flat model consists of a single, two-dimensional array of data elements, where all members of a given column are assumed to be similar values, and all members of a row are assumed to be related to one another. For instance, columns for name and password that might be used as a part of a system security database.
2. Hierarchical Model
   • Database resembles a tree like structure.
   • Implies a single upward link in each record to describe the nesting, and a sort field to keep the records in a particular order in each same-level list.
   • To create links between the records, the hierarchical model uses Parent Child Relationships.
   • This structure allows one 1:N relationship between two types of data.
   • One limitation of the hierarchical model is its inability to efficiently represent redundancy in data.
   • E.g. : Used in IBM’s IMS  DBMS
     
3. Network Model
   • The network model permitted the modeling of many-to-many relationships in data
   • The network model organizes data using two fundamental constructs, called records and sets. Records contain fields . Sets  define one-to-many relationships between records: one owner, many members. A record may be an owner in any number of sets, and a member in any number of sets.
   • The network model is able to represent redundancy in data more efficiently than in the hierarchical model.
   • E.g. : Used in IDS and IDMS
     
4. Relational Model
   • The basic data structure of the relational model is the table, where information about a particular entity (say, an employee) is represented in columns and rows (also called tuples).
   • The columns enumerate the various attributes of the entity (the employee’s name, address or phone number, for example), and a row is an actual instance of the entity (a specific employee) that is represented by the relation.
   • All relations (and, thus, tables) in a relational database have to adhere to some basic rules to qualify as relations. First, the ordering of columns is immaterial in a table. Second, there can’t be identical tuples or rows in a table. And third, each tuple will contain a single value for each of its attributes.
   • E.g. : IBM’s DB2, Informix, Oracle, Sybase, Microsoft’s Access, FoxBase, Paradox, Tandem ..
     
5. Object Oriented Model
   • Recent development, Stores data and methods to act on the data
   • E.g. : Objectstore and Versant
     
6. Dimensional Model
   • The dimensional model is a specialized adaptation of the relational model used to represent data in data warehouses in a way that data can be easily summarized using OLAP queries.
   • In the dimensional model, a database consists of a single large table of facts that are described using dimensions and measures. A dimension provides the context of a fact and is used in queries to group related facts together.
   • The dimensional model is often implemented on top of the relational model using a star schema, consisting of one table containing the facts and surrounding tables containing the dimensions.

 

What is a Database?

Some definitions of database –

“An organized collection of logically related data” McFadden – 1999

“A database is a self describing collection of integrated records” Kroenke 2002

Database is a shared organized collection of logically related persistent data.

A database defines a structure for storing information. Databases are typically organized into tables, which are collections of related items. You can think of a table as a grid of columns and rows.