Question

1- what are the stages for designing a database and explain them?

2- what is 3-layer ANSI-SPARC architecture, explain 3 advantages of it, and how does this architecture address the issue of data independence for a database system?

3- (a)what is the definition of Normalization ?

(b)why we use it?

(c) how does normalization assist in or reducing redundancie on a design database?

Answer 1

Answer:

(1) Stages of designing database:-

• Decide the reason of your database
• Discover and organize the data required
• logically devide infomrations into various tables and columns as one of its traits
• Specify the primary key for each table
• Set Up the relationship among various tables formed
• Redefine your design to take care of all the requirements
• Apply normalization technique to the tables

(2) 3 layer ANSI SPARC architecture has following layers

1. Internal layer :
   1. lowest lavel of data abstraction
   2. explains how data is stored in data storage also called as physical layer
2. Conceptual layer:
   1. Explains what data are stored in database
   2. relationship among those data
3. External layer:
   1. It represent a part of the database that end user is concerned about
   2. It is also known as view layer

Advantages of this model:

• It provides data abstractions
• same data can be accessed by different user according to his customizations
• The user is not been concerned with actual data storage within the system

Because data is abstracted into various layers such that above layer is not concerned how lower layer is functioning which provides data independence. Also same data can be accessed by different user according to his customizations.

(3) (a) Normalization: Normalization is the method of organizing information in a database. This incorporates making tables and setting up connections between those tables agreeing to rules planned both to protect the information and to form the database more adaptable by killing repetition and conflicting reliance

(b) Reason for using normalizations:-

• Reduction of duplicate data across tables
• Much more flexible database design
• A better handling of database security for example username and hashed password will be kept at a single place

(c) Normlaization forms are based on the premise that data should not be duplicatd, it should be kept at a single place and all the tables where that data is needed can be taken by creating relationship among the table. This underlying principle itself help in reducing data duplication and hence reducing redundancies on a design database.
While updating the records as well it is easir as a given data is present at a single location and not at multiple locations.

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