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Relation model concept and its advantage & disadvantage - Computer science fundamentals tutorial

    Relation model concept and it's advantage & disadvantage

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1.What is relational model?
  Ã˜ Relation model represent database as a collection of relations. A relation is nothing but a table of values. Every row in the table represents a collection of related data values. This row in the table denotes a real world entity or relationship.

     Relational model concept: -
  ·Attribute: -Each column in a table, Attributes is the properties which define a relation. Example: - DNO, DNAME.

  ·Table: - In the relational model relations are saved in the table format. A table has two properties rows, column. Rows represent records and column represents attributes.


  · Degree: - The total number of attribute which in the relation which called the degree of relation.

  ·Cardinality: -Total number of rows present in the table.

    Attribute domain: -Every attribute has some predefined values and scope which is known as attribute domain.

     Advantage of relational model: -
    1) Simplicity: - A relational data model is simpler than hierarchical model and network model.

    2) Easy to use: - The relational model is easy as table consisting of rows and column is quite natural and easy to understand.

    3) Data independence: - the structure of a database can be changed without having to change any application.

    4)   Query capability: -It make possible for a high level query language like SQL to avoid complex data navigation.

      Disadvantage of using relational model: -
   · Few relational databases have limits on field length which cannot be exceeded

   · Relational databases can sometime become complex as the amount of data grows and the relation between pieces of data become more complicated.     

     ·Complex relational database may lead isolated databases where information cannot be shared from one system to another. 
        
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