A flat file is a collection of data stored which usually contains one record per line or a physical record (for e.g. in a disk or tape). A comma separated data in Microsoft excel is a flat file. There are no structural relationships between the records. There are no formats applied to the data contained in a file and the comma at the end denotes the end of one field in a record. Each record is written on a line in the line, which allows all data for a single record to be stored separately. Flat file databases do not have to use a single flat file. Information about the orders of the customers can be stored in one flat file while the information regarding customers would be stored in the other flat file. These files are not related in any way, so the flat file database for customer information has no idea that any information exists about orders. To make them work all the relevant information about a record needs to be stored in the same file.
Advantages and disadvantages:
Flat file databases do have some uses but however the functionality of this data model is not efficient than the faster and structural approach. It would be really cumbersome to use when you have a lot of information that you want to cross check.
Examples are: name and address list with the field Name, Address, and Phone Number on a sheet of paper.
ï‚¢ Hierarchical - 1970s - 1990s
A hierarchical database model is a data model in which data is organized into a tree like structure. The structure allows repeating information using parent-child relationships. Each parent can have many children but one child can have only one parent. This is a 1:many ratio. All the attributes of a specific record are listed under an entity type.
Hierarchical Model
University
Management
Students
Staff
Accounting dept.
Rector
Labs
Hierarchical databases are fast and simple but inflexible, since the relationship is restricted to one to many, only allowing for one parent segment per child.
Advantages:
Navigating among the data is very fast because of the pointers (which points from one data record to another) which are used in the parent/child relationship.
Disadvantages:
The main disadvantage of hierarchical database is that it is very rigid. If one wants to add a field, then he has to make a new table first. Similarly if one wants to add a relationship then he must add a new and redundant database structure.
Example: IBM, s IMS system.
ï‚¢ Network - 1970s - 1990s
A database that runs in a network. It holds the addresses of other users in the network. It is a database organization that allows for data relationship in a network. A single data point can point to multiple data elements and itself can be pointed by other data elements.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Network_Model.jpg/320px-Network_Model.jpg
Disadvantages:
The network database model implements application in the data structure that limits the flexibility. In a network model data model are accesses one at a time. It lacks the structural independence.
Advantages:
The network model is simple and easy to design. One can access his/her work from any computer if it allows it to share files. It is high speed and efficient.
ï‚¢ Relational - 1980s - present
A relational database is a set of tables containing data fitted into predefined categories. It matches data by using common characteristics found within a data set. Each table contains one or more data categories in columns. Each row contains a unique data.
For example, a data containing all the real estate transactions can be grouped by the year each transaction occurred, the sale price and buyers name etc. Such grouping use relational models. Such a database is called "relational database". The software used is relational database management system (RDBMS).
Advantages:
Relational databases are currently important for storing data like financial records, medical records, personal information and etc. One of the advantages of this database is to link the information about a specific person who is in several databases together by simple links.
Disadvantages:
One of the disadvantages of this database is that when it is created it cannot be changed easily so any database forming as part of this database must be carefully planned
ï‚¢ Object-oriented - 1990s - present
An object oriented database management system (OODBMS) is a database in which information is represented in the form of objects and classes that supports the modelling and creation of data as objects. This includes classes and the inheritance properties and subclasses method and their objects.
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http://www.nlm.nih.gov/research/visible/vhp_conf/gingins/images/class_hi.gif
Advantages:
The code is easier to organize and maintain.
Chances of logic errors are less.
Code redundancy is avoided because of inheritance.
Unwanted code can be avoided easily.
ï‚¢ Object-relational - 1990s - present
An object relational database is a database management system similar to relational database but with an with an object oriented database model, objects, classes and inheritance. It supports extension of the data model. It can be said to provide middle ground between relational databases. The approach is same as in relational database but in this the data resides in the database and is manipulated collectively with queries in a query language.
ï‚¢ Data warehousing - 1980s - present
A data warehouse is a database used for reporting. The data passes through operational data store for additional operations before it is used in the DW for reporting. A data warehouse works in three layers 1) Staging 2) Integration 3) Access.
Staging is used to store a raw data for developers. The "integration layer" is used to integrate data. The "access" layer is for getting data out for users.
http://mybibeat.files.wordpress.com/2009/08/data-warehouse-architecture.png
Advantages:
Data warehouse enhance end users to a wide variety of data. It can be a significant enabler of commercial business, particularly customer relationship management systems.
ï‚¢ Web-enabled - 1990s - present
It is a database with a web-based interface. It provides access to business information and making queries, placing orders and records via internet and browser services.
Internet connects users of multiple platforms through an interface known as web browser. Acceptance of the internet by business has brought a lot of changes and a lot of completion for the manufacturers. Now customers can buy stuff directly from the manufacturers which save his money and time. Stuff from the internet can also be bought or auctioned which is more convenient. All these applications require a database support, which is the web-enabled database.
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