Components of the Database System Environment

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Components of the Database System Environment

There are five major components in the database system environment and their interrelationship  are –

  • Hardware
  • Software

    DBMS Application Users
    DBMS Application Users
  • Data
  • Users
  • Procedures

1. Hardware: The hardware is the actual computer system used for keeping and accessing the database.

2. Software: The software is the actual DBMS. Between the physical databases itself (i.e. the data as actually stored) and the users of the system is a layer of software, usually called the Database Management System or DBMS. All requests from users for access to the database are handled by the DBMS. One general function provided by the DBMS is thus the shielding of database users from complex hardware-level detail.

omponents of the Database System
omponents of the Database System

3. Data: It is the most important component of DBMS environment from the end users point of view. As shown in figure that data acts as a bridge between the machine components and the user components. The database contains the operational data and the meta-data, the ‘data about data’.

4. Users: There are a number of users who can access or retrieve data on demand using the applications and interfaces provided by the DBMS. Each type of user needs different software capabilities. The users of a database system can be classified in the following groups, depending on their degrees of expertise or the mode of their interactions with the DBMS. The users can be:

• Naive Users

• Online Users

• Application Programmers

• Sophisticated Users

• Data Base Administrator (DBA)

5. Procedures: Procedures refer to the instructions and rules that govern the design and use of the database. The users of the system and the staff that manage the database require documented procedures on how to use or run the system.

These may consist of instructions on how to:

• Log on to the DBMS.

• Use a particular DBMS facility or application program.

• Start and stop the DBMS.

• Make backup copies of the database.

• Handle hardware or software failures.

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DATABASE MANAGEMENT SYSTEM

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WHAT IS DATABASE MANAGEMENT SYSTEM?
The Database Management System is to provide a convenient and efficient way to store and retrieve data stored in a database.
A  database  is  a  computer  generated  software  program  which can  be  used  to  access  the  data  stored  in  database  in  an organized manner.
The  term database is  a  structured  collection  of  data  stored which  can  be  stored  in digital  form.  Before  the  actual  data  is stored in the database, we should clearly specify the schema of the  database  and  different  techniques  used  to  manipulate  the data stored in a database.
DBMS must provide efficient techniques in order to protect the data from accidental system crashes.

WHERE IS DATABASE MANAGEMENT SYSTEM USED?
DBMS systems can be used extensively in the following fields –
1. Transportation: DBMS system can be used for reservation or cancellation  of  tickets  and  can  be  also  used  to  check  for  the schedules of incoming and outgoing flights.
2. Education: DBMS system can be used by different universities to allow students take admission online, checking the status of vacant seats, enrolment system can be done computerized etc.
3. Banking: DBMS system has completely changed the face of the banking sector. Few decades ago, the banking system was purely the paper based system have now transformed in keeping less of paper work.
4. Sales: DBMS system allows the data to be stored in electronic format by making use of relational databases which allows the data to be stored in highly organized manner.  This database allows the information such as information about the customers, products, sales, purchases etc to be stored in database.
5. Manufacturing: DBMS  system  allows  the  user  to  store information about the production of good, the inventory details, the total number of orders, supply chain information in database so that it allows the decision makers to make critical decisions in timely manner.
6. Human Resource: DBMS has made the life of HR team much better  by  allowing  the  team  to  compute  tax  deductions, employee  wages,  retrieving  the  details  of  the  employees in faster manner as compared to traditional paper based approach which was time consuming.

DBMS Applications
DBMS Applications

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Database

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WHAT IS DATABASE?
Database is collection of data which is related by some aspect. Data is collection of facts and figures which can be processed to produce information. Name of a student, age, class and her subjects can be counted as data for recording purposes.

WHAT ARE THE FEATURES OF DBMS?

Real-world entity: Modern DBMS are more realistic and uses real world entities to design its architecture. It uses the behavior and attributes too. For example, a school database may use student as entity and their age as their attribute.
Relation-based tables: DBMS allows entities and relations among them to form as tables. This eases the concept of data saving. A user can understand the architecture of database just by looking at table names etc.
Isolation of data and application: A database system is entirely different than its data. DBMS stores metadata which is data about data, to ease its own process.
Less redundancy: DBMS follows rules of normalization, which splits a relation when any of its attributes is having redundancy in values. Following normalization, which itself is a mathematically rich and scientific process, make the entire database to contain as less redundancy as possible.
Consistency: DBMS always enjoy the state on consistency where the previous form of data storing applications like file processing does not guarantee this. Consistency is a state where every relation in database remains consistent.
Query Language: DBMS is equipped with query language, which makes it more efficient to retrieve and manipulate data. A user can apply as many and different filtering options, as he or she wants. Traditionally it was not possible where file-processing system was used.
ACID Properties: DBMS follows the concepts for ACID properties, which stands for Atomicity, Consistency, Isolation and Durability. These concepts are applied on transactions, which manipulate data in database.
Multiuser and Concurrent Access: DBMS support multi-user environment and allows them to access and manipulate data in parallel. Though there are restrictions on transactions when they attempt to handle same data item, but users are always unaware of them.
Multiple views: DBMS offers multiples views for different users. A user who is in sales department will have a different view of database than a person working in production department. This enables user to have a concentrate view of database according to their requirements.
Security: Features like multiple views offers security at some extent where users are unable to access data of other users and departments.

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SQL is Structured Query Language

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What is SQL?
SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in relational database.

SQL is the standard language for Relation Database System. All relational database management systems like MySQL, MS Access, and Oracle, Sybase, Informix, postgres and SQL Server use SQL as standard database language.

Why SQL?
Allows users to access data in relational database management systems.
Allows users to describe the data.
Allows users to define the data in database and manipulate that data.
Allows embedding within other languages using SQL modules, libraries & pre-compilers.
Allows users to create and drop databases and tables.
Allows users to create view, stored procedure, functions in a database.
Allows users to set permissions on tables, procedures, and views

How the SQL Process work?
When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task.
There are various components included in the process. These components are Query Dispatcher, Optimization Engines, Classic Query Engine and SQL Query Engine, etc. Classic query engine handles all non-SQL queries but SQL query engine won’t handle logical files.
Following is a simple diagram showing SQL Architecture:

Structured Query Language
SQL Process

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Validation Groups:

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Validation Groups:

Complex pages have different groups of information provided in different panels. In such a situation a need for performing validation separately for separate group, might arise. This kind of situation is handled using validation groups. To create a validation group, you should put the input controls and the validation controls into the same logical group by setting their ValidationGroup property.

Example:
The following example describes a form to be filled up by all the students of a school, divided into four houses, for electing the school president. We will be using the validation controls to validate the user input.

The content file code:

Candidate:

Please Choose a Candidate
M H Kabir
Steve Taylor
John Abraham
Venus Williams

House:

Red
Blue
Yellow
Green

Class:
Email:

The code behind the submit button:
protected void btnsubmit_Click(object sender, EventArgs e)
{
if (Page.IsValid)
{ lblmsg.Text = “Thank You”; }
else
{ lblmsg.Text = “Fill up all the fields”; }}

The Validation Control Classes

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The BaseValidator Class:
The validation control classes inherit from the BaseValidator class and inherit its properties and methods. Therefore, it would help to take a look at the properties and the methods of this base class, which are common for all the validation controls:
Members Description
ControlToValidate Indicates the input control to validate.
Display Indicates how the error message is shown.
EnableClientScript Indicates whether client side validation will take.
Enabled Enables or disables the validator.
ErrorMessage Error string.
Text Error text to be shown if validation fails.
IsValid Indicates whether the value of the control is valid.
SetFocusOnError It indicates whether in case of an invalid control, the focus should switch to the related input control.
ValidationGroup The logical group of multiple validators, where this control belongs.
Validate() This method revalidates the control and updates the IsValid property.

The RequiredFieldValidator:
The RequiredFieldValidator control ensures that the required field is not empty. It is generally tied to a text box to force input into the text box.
The syntax for the control:

The RangeValidator:
The RangeValidator control verifies that the input value falls within a predetermined range.
It has three specific properties:
Properties Description
Type it defines the type of the data; the available values are: Currency, Date, Double, Integer and String
MinimumValue it specifies the minimum value of the range
MaximumValue it specifies the maximum value of the range

The syntax for the control:

The CompareValidator:
The CompareValidator control compares a value in one control with a fixed value, or, a value in another control.
It has the following specific properties:
Properties Description
Type it specifies the data type
ControlToCompare it specifies the value of the input control to compare with
ValueToCompare it specifies the constant value to compare with
Operator it specifies the comparison operator, the available values are: Equal, NotEqual, GreaterThan, GreaterThanEqual, LessThan, LessThanEqual and DataTypeCheck

The basic syntax for the control:

The RegularExpressionValidator
The RegularExpressionValidator allows validating the input text by matching against a pattern against a regular expression. The regular expression is set in the ValidationExpression property.
The following table summarizes the commonly used syntax constructs for regular expressions:
Character Escapes Description
\b Matches a backspace
\t Matches a tab
\r Matches a carriage return
\v Matches a vertical tab
\f Matches a form feed
\n Matches a new line
\ Escape character
Apart from single character match, a class of characters could be specified that can be matched, called the meta characters.
Metacharacters Description
. Matches any character except \n
[abcd] Matches any character in the set
[^abcd] Excludes any character in the set
[2-7a-mA-M] Matches any character specified in the range
\w Matches any alphanumeric character and underscore
\W Matches any non-word character
\s Matches whitespace characters like, space, tab, new line etc.
\S Matches any non-whitespace character
\d Matches any decimal character
\D Matches any non-decimal character
Quantifiers could be added to specify number of times a character could appear
Quantifier Description
* Zero or more matches
+ One or more matches
? Zero or one matches
{N} N matches
{N,} N or more matches
{N,M} Between N and M matches
The syntax for the control:

VALIDATION CONTROL

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VALIDATION CONTROL: INTRODUCTION
 ASP.NET provides six validations controls that can be used to validate the data on a web form and validate the user input data to ensure that useless, unauthenticated or contradictory data does not get stored.
 This validation controls can be used with HTML and Web Server controls. Six validation controls are available with ASP.NET as of now, they are as follows –
The RequiredFieldValidator Control – Ensures that the user does not skip a mandatory entry field.
The CompareValidator Control – Compares one controls value with another controls value, constants and data type using a comparison operator (equals, greater than, less than, and so on).
The RangeValidator Control – Checks the user’s input is in a given range (eg: numbers or characters).
The RegularExpressionValidator Control – Checks that the user’s entry matches a pattern defined by a regular expression.
The CustomValidator Control – Checks the user’s entry using custom-coded validation logic.
The ValidationSummary Control – Displays a summary of all validation errors inline on a web page, in a message box, or both.