DATA MODEL

 DATA MODEL

It is a conceptual tools which describe logical design of a database. It define entity definations, relationship and symmentic properties of intigrity constant.The very first data model could be flat data-models, where all the data used are to be kept in the same plane. Earlier data models were not so scientific, hence they were prone to introduce lots of duplication and update anomalies. While the Relational Model is the most widely used database model, there are other models too:

  • Hierarchical Model
  • Network Model
  • Entity-relationship Model
  • Relational Model

  • Hierarchical Model

    This database model organises data into a tree-like-structure, with a single root, to which all the other data is linked. The heirarchy starts from the Root data, and expands like a tree, adding child nodes to the parent nodes.

    In this model, a child node will only have a single parent node.

    This model efficiently describes many real-world relationships like index of a book, recipes etc.

    In hierarchical model, data is organised into tree-like structure with one one-to-many relationship between two different types of data, for example, one department can have many courses, many professors and of-course many students .

  •        




Network Model

This is an extension of the Hierarchical model. In this model data is organised more like a graph, and are allowed to have more than one parent node.

In this database model data is more related as more relationships are established in this database model. Also, as the data is more related, hence accessing the data is also easier and fast. This database model was used to map many-to-many data relationships.

This was the most widely used database model, before Relational Model was introduced.


Entity-Relationship Model

Entity-Relationship (ER) Model is based on the notion of real-world entities and relationships among them. While formulating real-world scenario into the database model, the ER Model creates entity set, relationship set, general attributes and constraints.

ER Model is best used for the conceptual design of a database.



Relational Model

The most popular data model in DBMS is the Relational Model. It is more scientific a model than others. This model is based on first-order predicate logic and defines a table as an n-ary relation.








Comments

Post a Comment

Popular posts from this blog

Introduction of C Language

Image
Hello Friends, Here we will know some basics of C Language. So let's Start...... C Programming C is a powerful general-purpose programming language. It is fast, portable and available in all platforms. If you are new to programming, C is a good choice to start your programming journey. C  is a procedural programming language. It was initially developed by Dennis Ritchie in the year 1972. It was mainly developed as a system programming language to write an operating system. The main features of C language include low-level access to memory, a simple set of keywords, and clean style, these features make C language suitable for system programmings like an operating system or compiler development. Many later languages have borrowed syntax/features directly or indirectly from C language. Like syntax of Java, PHP, JavaScript, and many other languages are mainly based on C language. C++ is nearly a superset of C language (There are few programs that may compil...
Read more

First in C programming

                First C Program  To write the first c program, open the C console and write the following code: #include <stdio.h>      int  main(){     printf( "Hello C Language" );     return  0;    }   #include <stdio.h> includes the standard input output library functions. The printf() function is defined in stdio.h . int main() The main() function is the entry point of every program in c language. To compile and run the c program, by menu and by shortcut. By shortcut key Press ctrl+f9 keys compile and run the program directly. User will see the output on the screen by pressing the alt+f5keys. Now, press Esc to return the turbo c++ console.  printf and scanf is in lowercase because it is a keywords. Keywords is a set of reserved words. All keywords...
Read more

Computer generation

Image
                Computer Generation 1st generation The period of 1st generation was 1942-1954. The main features are- *Vaccum tube technology *Unreliable *Supported Machine Language Only *Very Costly *Generate lot of heat *Need A.C *Non Portable *Consumed lot of Electricity 2nd Generation The period of second generation was 1952-1964. The main features are- *Use of transistor *Reliable as compared to first generation computer *Smaller size as compared to first generation *Consumed less electricity *Faster than first generation *Still very Costly *Support machine and assembly language *A.C needed   3rd generation The period of third generation was1964-1972. *The main features are- *Use of integrated circuit *More reliable *Smaller size *Generate less heat *Faster *Still costly *A.C needed *Consumed lesser electricity 4th generation The period of fourth generation was 1972-1990. The...
Read more