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.
- 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.
- 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
- 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
- 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 ..
- Object Oriented Model
- Recent development, Stores data and methods to act on the data
- E.g. : Objectstore and Versant
- 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.
March 5, 2009 at 10:42 am
I like your definitions, and it is organized well. But you forgot to mention Key/Value pairs used in website databases such as Amazon.