Database Model

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Database Model

This way in which information is sub devised and managed within a database is refereed as data model. Each DBMS is based on data models. The data models can be classification into three major group

1. Hierarchical Database Model
2. Network Database Model
3. Relational Database Model

1. Hierarchical Database Model

It organized data is a tree structure, their is hierarchy of parent and child sequence. This structure implied that a record can help replicated information generally child  data segment. It increases data redundancy as a result of which it is not used often but it is easy to implement due to its limited rules. Hierarchical database technology is used for high-volume transaction processing and MIS (Management Information System) applications. Few new database are developed with hierarchical DBMSs since newer applications tend to have broader needs than simply translation processing of summarization of transaction data. 

Advantage 

• It is the easiest model of database
• A database owner is more secured because nobody else can see and modify a child without consulting to its parent.
• Searching is fast and easy, if parent is known.
• Very efficient in handling 'one-to many' relationship.

Disadvantage

• It is old fashioned, outdated database model.
• Modification and addition of child without consulting the parent is impossible or very hard. So, it is not-flexible database model.
• Can't handle 'many-to-many' relationship.
• Increases redundancy because same data is to be written in different places.

2. Network Database Model

It is more flexible then hierarchical data model. It accepts any relationship searching is faster because multidirectional pointer is available. This model is less secure in comparison to hierarchical model because it is open to a network model that are used for high volume transition processing application.  Network system still require significant programming and database design knowledge and time and hence are used primarily in those organizations with significant expertise with such technologies. 

 

Advantage

• More flexible then hierarchical because accepts many-to-many relationship.
• Reduces redundancy because data shouldn't be repeated if same of data is needed. For such case, a parent can have more than one virtual parents and one real parent. 
• Searching is faster because of multidirectional pointers.

Disadvantage

• Very complex type of database model.
• Needs long programs to handle the relationship.
• Pointers needed in the database model causes increased maintenance time.
• Less security in comparison to hierarchical model, because it is open to all.

          

3. Relational Model

In a relational data model, unlike the hierarchical and Network model are no physical linked. All data is maintains in the form of tables. i.e. relation consisting of rows  and column. Each row represent and entity (record). The relationship between two tables is implemented through common attribute in the table. The query in relational model are very similar then hierarchical and network model. 

Advantage

• Since one table is linked with other with some common fields, rules implemented on one table can easily be implemented to another.
• Some rules, popularly known as referential integrity, can easily be implemented.
• Very less redundancy. 
• Normalization of database is possible.
• Rapid database processing is possible.

Disadvantage

• It is more complex than other models.
• Too many rules makes database not-user-friendly.