In class 12 unit 2 Student must study 4 major types of database models these are Hierarchical, Network, Relational, Entity Relation Database Models.
Hierarchical database model
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Oldest types of database models
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Data represented in the form or records
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All the data represented in the tree format.
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The relationship between the records is called the parent-child relationship in which any child record relates to only a single parent type record.
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In this database system, the parent is top-level privileges, and the child is bottom-level privileges.
Advantage
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It is the easiest models
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It has one or more attributes
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The searching is cast and easy if a parent is known
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It supports one to one and one to many relationships
Dis Advantages
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Outdated database model
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It does not support many to many relationships the dependency on the parent node is not beneficial always.
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Depends on the parent node is not beneficial always.
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Increases redundancy.
Network database models.
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This is an extension of the Hierarchical model.
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Data is organized more like a graph and is allowed to have more than one parent node.
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In this database model data is more related as more relationships are established in this database model.
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A network database model consists of a collection of records that are interrelated to each other which the help of relationship.
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Each record has multiple fields and each field has only one data value.
Advantages of network database model
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It accepts many to many relationships so it is more flexible
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The searching is faster because of multidirectional pointers
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The networks model is simple and easy to design
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It reduces redundancy because data should not be repeated if the same data is needed.
Disadvantages of network database models
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It is difficult to handle the relationship in complex programs
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There is less security because of sharing data.
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It increases the processing overhead due to the complex relationship.
Relational Database Model
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In this model data present in the table.
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A relational database contains one or more data categories in columns, also called attributes.
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Each row, also called a record or tuple(a data structure consisting of multiple parts), contains a unique instance of data, or key, for the categories defined by the columns.
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Each table has a unique primary key, which identifies the information in a table.
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The relationship between tables can then be set via the use of foreign keys -- a field in a table that links to the primary key of another table.
Advantage of Relational database model
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The breaking of a complex database table into a simple database table becomes possible.
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Database processing faster than other models.
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There is very low redundancy
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The integrity rules can easily be implemented.
Disadvantages
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It is more complex than other models
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There are too many rules because of the complex relationship
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It needs more powerful computers and data storage devices.
Entity-Relationship Database Model
ER database model is based on a perception of a real-world that contains a collection of basic objects called entities and of the relationships among these objects and characteristics of an entity.
ER- database is an overall logical structure of a database that can be expressed graphically.
ER models, also called an ER schema, are represented by ER diagrams.
ER modeling is based on two concepts:
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Entities, defined as tables that hold specific information (data)
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Relationships, defined as the associations or interactions between entities
Components of ER Database models:
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Entity: things, objects, or sets of properties. Donate by rectangle
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Attribute: properties of an entity, element. Donate by oval
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Link: the flow of information. Donate by line
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Relationship: relation between several entities. Done by a diamond shape.
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