ICS Part 2 Computer Lectures Chapter 1 Data Basics Database Model and types of Model
1)Database Model
i) Hierarchical Model
ii) Network Model
iii) Relational Model
2) Now So Let's Start For Practical With Example
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What is Hierarchical Model
In the hierarchical model, the data is stored in the tree-like structure in which there is a root node where the data is started to store. The sort field is used for the sibling record to maintain some order while storing data in the hierarchical model. The hierarchical database model is mostly used when there is a need for maintaining an information management system. In this database model there exist a one-to-many relationship among data. The retrieval of data has a different technique in the hierarchical model.
The technique follows navigating a downward direction using the pointers so that data can be accessed sequentially. Because of this technique, has a disadvantage as it is not capable of handling all types of database operations. The retrieval time of data is more compare to other types of database models. The records are not connected to the hierarchical model. And the model consists of an upward link that is used to represent the hierarchy of data stored in the database system.
What is NETWORK MODEL?
The network structure database model has a very similar structure as compared to the hierarchical model. This model allows a many-to-many relationship in the tree-like structure model. It means there can be multiple parents. The network model uses the two fundamental concepts i.e. sets and records. The records contain file which can be in hierarchical form and sets which are used to define the many-to-many relationship among the records. The set uses the circular linked in DATA STRUCTURE which one record which is a parent can appear once in a circle and the child of that particular parent can appear more than once in each circle.
In the network database model, the records are connected to each other. In this manner, the hierarchy is maintained among the records. The data access in this database model is either in sequential form or can be in a circular linked list pattern. And there can be multiple paths to access to any particular record. The disadvantage of this network model is that it contains redundancy among the records which means one record can appear more than one time in the database model.
What is RELATIONAL MODEL?
The relational database model is designed to remove the dependency in the database management system. The development of the relational database model is targeted for mostly microcomputer systems. The three keys which are used in relational database models are domains, attributes, and relations. The relation is defined as a table that contains rows and columns. The columns present in the table are called attributes in And the domain is defined as a set of values that can be inserted in the database model. The data structure used is a table in this model and the data is stored in the form of rows and columns in the model. The rows are also known as tuples.
For example, there is a relation named employee details. It can have multiple attributes like name, age, gender. And there can be multiple tuples for one single relation named as employee details. The key which can be used to uniquely identify any row is called the primary key. And these keys can be used to join more than one table at the same time. For example, there can be a column named location in the employee table and the column location can be the primary key of the location table.
By this key, the two table location table and employee table can join and the operations can be performed on the join table. The relational database model uses the structured query language (SQL) to perform operations on the database system. The relational model contains multiple tables which look like flat database model. One of the key advantages of this model is whenever the value appears more than on time in two different records there exist some relationships among them.
Computer Lecturer: Shahzaib Naz
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