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Outlines

• File Systems
• —Database Management Systems
• Purpose of Database Systems
• Database Objects
• —Insert data into table
• Database Constraints

File systems

File System has duplication

File can not be centralized resource
File can not be used as distributed computing.
Apply constraint strategy is too difficult.
Database Management System
DBMS contains information about a particular enterprise

Collection of tables

An environment that is both convenient and efficient to use
Database Applications

Banking: all transactions

Airlines: reservations, schedules

Universities:  registration, grades

Sales: customers, products, purchases

Online retailers: order tracking, customized recommendations

Manufacturing: production, inventory, orders, supply chain

Human resources:  employee records, salaries, tax deductions

Purpose of Database Systems

Database is solution of all drawbacks

— Drawbacks of using file systems to store data:

  Separation and isolation of data

  Duplication of data.

           Data dependence.  

Database Objects  
How to create database

—How to create the tables
How to create fields , records
Example:
Create database dem0;
Examples:
Create database demo;

Use demo
Create table emp(id int, name varchar(100))
 

—

Insert the data into table   

Insert into emp values(1,’admin’)

Insert into emp values(1,’ali’)
Allow the duplication

Database Constraints 

To prevent invalid data entry into tables..
1.Primary key
2.Not Null
3.Check
4.Unique
5.Foreign Key
 

Constraint Description

NOT NULL: Specifies that the column cannot contain a null value 
UNIQUE: Specifies a column or combination of columns whose values must be unique for all rows in the table.

PRIMARY KEY: Uniquely identifies each row of the table

FOREIGN KEY: Establishes and enforces a foreign key relationship between the column and a column of the referenced table

CHECK: Specifies a condition that must be true

Example:
sql management studio query

Create table persons

(p_id int primary key,

first_name varchar(100) not null,

Last_name varchar(100),

Adress varchar(255) unique,

Check(p_id>0))

 

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