What is a Database, Types and Models of Databases

WHAT IS A DATABASE?

A database is an organized collection of data typically stored in electronic format, it allows you to input, manage, organize and retrieve data quickly.

A data base are traditionally organized by records (row), fields (columns) stored in a table which are stored in a database file. This tables are collections of rows and columns that is used to organize information about a single topic. Each row corresponds to a single record and contains several attributes that describes the row.

There are two types of the databases namely;

The analytic database: these are primarily static, read only databases which stored archived, historical databases use for analysis.

The operational database:  these are used to manage more dynamic bits of data. This database allows you to do more than just view simply archived data. Operational databases allows you to modify the data. (Selena Sol, 2003)

DATABASE MODELS

Database models defines the logical structure and design of how the data is represented. The models describes the relationship between different part of the data

We have various database models

• The flat file model
• The relational model
• The network model
• The hierarchical model

Based on this post I will basically discuss on the network model and hierarchical model.

Before the 1980s, the two most commonly used database models are the network and hierarchical model (Selena Sol, 2003)

Hierarchical model:

This is a model in which record types are linked in a treelike structure. In this tree a single data acts as the root of the database from which other tables branch out.

This model can also be seen as a parent to child relationship in which each entity has only one parent but several children and at the top of the hierarchy there is only one entity which is regarded as the root. And the parent and children are tied together by links called pointer, a parent will have a list of pointers to each of their children.

(Image source, Google images)

 The hierarchical model, is more efficient than the flat-file model because there is not as much need for redundant data. If there is a need for change in the data, the change can only need to be processed once unlike the flat file model.

The hierarchical database model also has it disadvantages. For one, you cannot add a record to a child table until it has already been incorporated into the parent table. You might encounter difficulties, for instance, you wanted to add a student who had not yet signed up for any courses. Worse, yet, the hierarchical database model still creates repetition of data within the database. You might imagine that in the database system shown above, there may be a higher level that includes multiple course. In this case, there could be redundancy because students would be enrolled in several courses and thus each "course tree" would have redundant student information.

NETWORK MODEL

(Image source, Google images)

The Network Database model was created to give solution to some of the more serious problems with the Hierarchical Database Model.

The Network model solves the problem of data redundancy by representing relationships in terms of sets rather than hierarchy. The network model is very similar to the hierarchical model actually. In fact, the hierarchical model is a subclass of the network model. However, instead of using a single-parent tree hierarchy, the network model uses set theory to provide a tree-like hierarchy with the exception that child tables were allowed to have more than one parent. This allowed the network model to support many-to-many relationships. A Network Database looks visually like a hierarchical Database in that you can see it as a type of tree. However, in the case of a Network Database, the look is more like several trees which share branches. Thus, children can have multiple parents and parents can have multiple children.

The network database model also has its imperfection like:

Making structural changes to the database is not easy in the network model as the data access method is navigational. Any changes made to the database structure require the applications program to be modified before they can access data. Though the network model achieves data independence, it still fails to achieve structural independence.

The network model is also difficult to implement and maintain. Most implementations of the network model were used by computer programmers rather than real users. (Tabu llyas, 2015)

Advantages of the network data base mode to the hierarchical database model

1. The network model has a many-to-many relationship while the hierarchical has a one to many relationship.
2. In the network model the information can be easily accessed because of the link between the information but in the hierarchical model there is difficulty to navigate because of its owner to member connection.
3. There is also great flexibility among the information files because of the multiple relationships among the file unlike the hierarchical model there is less flexibility with the collection of information because of the hierarchical position of the files ( computingbusinessresearch.com)

References

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Available at: http://www.britannica.com/EBchecked/topic/130675/computer-science/21960/Types-of-database-models
[Accessed 4 march 2015].

Lyas, T., 2015. the advantages and disadvantages of the network model. [Online]
Available at: http://www.answers.com/Q/The_advantages_and_disadvantages_of_database_network_model
[Accessed 4 march 2015].

Macdonald, S., 2005. Hierarchical Database Model. [Online]
Available at: https://images.search.yahoo.com/images/view;_ylt=AwrB8psnDvZUp0kAIvmJzbkF;_ylu=X3oDMTIyazVmdTRqBHNlYwNzcgRzbGsDaW1nBG9pZANjMzYyOWU1NmZhNjc2ZTliNzEzYTIzMzc5MGE0NGUxZgRncG9zAzIEaXQDYmluZw--?.origin=&back=https%3A%2F%2Fimages.search.yahoo.com%2Fyhs%2Fsearch%
[Accessed 03 03 2015].

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