Introduction To Database Management Systems

Introduction To Database Management Systems

DESIGNING RELATIONAL DATABASE SYSTEMS

 Relational concepts

Any company has information needs. Assume this information a list of  employees, department, and salary, project, .accompany maintain information about employees, departments, salary's. These pieces of information called data

- Database concepts

 A database can be defined as collection of information, meaningfull data. The benefit of storing information in a database is to have a point of reference to be understood  and to make data easy to access and manage.

-Database management system

To handle a database professionally, you need database management system. A DBMS is a system that stores, modifies, and retrieves data in the database on request.  

-Database type

1- Network

2- Hierarchical

3- Relational

4- Object relational

Relational database definition -

1-A relational database is collection of relation

2-Two tables .a relational database use these two tables to store information 

-Relational database module components

1- Data integrity rules

2-collection of objects or relations

3-set of operators

-SQL definition

 Programming language it used to collect data from relational database (structured query language (SQL))

Stander language for operation on relation database

- RDBMS 

A relation database mangment system (RDBMS) is database management system (DBMS) that is based on the relational model as introduced by Dr. Edgar F.Codd

 OR We can said RDBMS manages a collection of tables 

-Access data in relational database

A user who wants to access data in the relation database executes SQL statements to send requests to the database.

 Relational Database Terms

A relation database can contain one or many tables. A table holds the data about something in the real world, such as employees.

For Example the EMP Table contains information about employees.

In the EMP table might include employee number, first name, last name, job, manager number, salary, and department number.

  

What's the structure Elements of TABLE ?   (EXM: EMP TABLE)

2- Column a column, or attribute, represent all data regarding one specific characteristic about employee .a column can contain primary key, foreign key, or non-key values. 

3- Primary key. The EMP column represents a primary key column for the EMP table.

Each row must contain a value in this column, and the value cannot be duplicate.

4- Foreign Key. The DEPTNO column shows the department number an represents a foreign key for the EMP table .A foreign key for the EMP table .A foreign key defines how one table relates to another.

5- NOT A KEY VALUE. IN the EMP table, the MGR column represents a column that is not a key value. Values don’t have to be unique or refer to unique values in another table.

6- A field is the point of intersection of a row and column .there can be only one value in field

7- NULL VALUE .A field can have no value in it .these called a null value.

8 – VALUES AND NULL VALUES. Same the column COMM it can continent value or null

System development life Cycle

You can develop a database by using the system development life cycle .this top-down ,systematic approach to database design is used to transform business information requirements into an operational database.

- The system development include

1- Strategy and analysis. In these phase you study and analyze business requirements.You interview the users and managers to identify the information requirements

2- Design. In these phase you design the database based on the model developed in the    analysis phase.

3- Build and document. In these phase you build the prototype system .you write and execute the commands to create the tables and supporting objects for the database 

4- Transition. In these phase you refine the prototype. You carry out user acceptance testing. And any modification to the prototype system.

 5- Production. You deliver the system to the users and operate the production system. After monitoring system performance  

  

Entity Relationship model Components
 

Models help communicate the concepts in people's minds. For example engineers build a model of home to work out any details before putting it into production .in same system designers develop models to explore ideas and improve their understanding of database design.

- Entity relationship model

Entity relationship (ER) modeling is commonly used by database designers during the strategy and analysis phase of the system development cycle.An ER model is an illustration of the various entities in a business and the relationships between those entities.

Components of ER model-

 

 1- Entities

 2- Attributes

 3- Relationship