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What is a Data Base?

A database is a computerized record keeping system. More completely, it is a system involving data, the hardware that physically stores that data, the software that utilizes the hardware’s file system in order to 1) store the data and 2) provide a standardized method for retrieving or changing the data, and finally, the users who turn the data into information.

What is Data Model?

A Data Model is to apply a structure and organization to a large chunk of data. It makes the data Easier to use management. access and easier to understand.

• File system  : Is to store a data files such as text or binary file in file stem such as windows explorer or UNIX file.
• Hierarchical Databases  :  In a hierarchical data model, data are organized into a tree-like structure. The structure allows repeating information using parent/child relationships: each parent can have many children but each child only has one parent. All attributes of a specific record are listed under an entity type. In a database, an entity type is the equivalent of a table; each individual record is represented as a row and an attribute as a column. Hierarchical structures were widely used in the first mainframe database management systems.
• Network Database  :  The network model is a database model conceived as a flexible way of representing objects and their relationships. Where the hierarchical model structures data as a tree of records, with each record having one parent record and many children, the network model allows each record to have multiple parent and child records, forming a lattice structure.The chief argument in favor of the network model, in comparison to the hierarchic model, was that it allowed a more natural modeling of relationships between entities. Although the model was widely implemented and used, it failed to become dominant for two main reasons. Firstly, IBM chose to stick to the hierarchical model with semi-network extensions in their established products such as IMS and DL/I. Secondly, it was eventually displaced by the relational model, which offered a higher-level, more declarative interface.
• Relational Database  :  A relational database is a database that conforms to the relational model, and could also be defined as a set of relations or a database built in an RDBMS.
• Object Database  :  In an object oriented database, information is represented in the form of objects as used in Object-Oriented Programming. When database capabilities are combined with object programming language capabilities, the result is an object database management system (ODBMS). An ODBMS extends the programming language with transparently persistent data, concurrency control, data recovery, associative queries, and other capabilities.Some object-oriented databases are designed to work well with object-oriented programming languages such as Java, C#, Visual Basic .NET, C++ and Smalltalk. Object databases are generally recommended when there is a business need for high performance processing on complex data.
• Object-Relational Database  :  An object-relational database (ORD) or object-relational database management system (ORDBMS) is a relational database management system that allows developers to integrate the database with their own custom data types and methods. The term object-relational database is sometimes used to describe external software products running over traditional DBMSs to provide similar features; these systems are more correctly referred to as object-relational mapping systems.Whereas RDBMS or SQL-DBMS products focused on the efficient management of data drawn from a limited set of data types (defined by the relevant language standards), an object-relational DBMS allows software developers to integrate their own types and the methods that apply to them into the DBMS. The goal of ORDBMS technology is to allow developers to raise the level of abstraction at which they view the problem domain.

Normalization

Normalization is a process of simplifying the relationship between data elements in a record. Its is the transformation of complex data stores to set of smaller, stable data structures. Normalized data structures are simpler, more stable and are easier to maintain. Normalization can therefore be defined as a process of simplifying the relationship between data elements in a record.

Is key factor in DB design. The normalization rules are designed to prevent update anomalies and data inconsistencies.

• Avoids duplication of data
• Makes data input more efficient
• Spreads data across multiple tables
• Generally makes data retrieval less efficient
• Based on E.F. Codd’s normal forms ( Rules about data storage)

Storage Situation

ID	First name	Last Name	Address	City
4575	Janet	Gale	786lee St	Franklin
4545	Lauren	Nicole	123 Main	Nashville
2121	Mark	Thomas	435 Elm	Jackson

How do we deal with a Second address?

ID	First name	Last Name	Address	Address2	city
4575	Janet	Gale	786lee St		Franklin
4545	Lauren	Nicole	123 Main		Nashville
2121	mark	Thomas	435 Elm		Jackson
6654	Bell	smith	45 elm	875 spike	Nashville

This causes the database to store empty space

 

Normalization

ID	First name	Last Name	Address	city
4575	Janet	Gale	786lee St	Franklin
4545	Lauren	Nicole	123 Main	Nashville
2121	Mark	Thomas	435 Elm	Jackson
6654	Bell	smith	45 elm	Nashville

 

ID	Addrerss2
6654	875 spike