The Development Of Software Engineering

The aim of introduction to state of the art software engineering techniques which are now of practical utility and which can be applied immediately in practical software project.I have already discussed SDLC in the previous article. By the end of this article you will learn fallowing things:
1. What is Software Engineering
2.Why Software Engineering
3.Types of Software Engineering
4. The characteristics of "good software"
5. The development of Software Engineering

Software Engineering:
Software Engineering  is concerned with building software systems which are large than would normally be tackled by a single individual,uses engineering principles in the development of these systems and is made up of both technical and non-technical aspects.

Here software means program and other operating information used by a computer,Engineering means the application of scientific methods to design,building,and use of tools,machines,constructions,and so on...

An engineering discipline that includes all 10 points as part of process and products in software engineering today.

Types of Software:

Now a days, types of software comes in many categories,some of which overlap also.

Why Software Engineering:

The purpose of  software engineering,software is often found in products and situations where very high reliability is expected,even under demanding conditions,such as monitoring and controlling nuclear power plants,or keeping a modern airline aloft,such applications contains millions of line of code,making them comparable in complexity to the most complex modern machines.

What is good Software:

The major problem encountered in development of large software systems:
Correctness,efficiency,interfacespecification,reliability,flexibility,documentation,maintainability and project organization.

User view where the quality is fitness for purpose

1. The Quality of the product
2. The Quality of the Process
3. The Quality of the service
4. The Quality of the Context of Business Environment

The Development of Software Engineering:

The software engineering has both positive and negative results in the past.However,software is not without its problems.Often Software System function,but not exactly as expected. Software engineers must understand that technical quality and business quality may be very different.

The fallowing are the Development of Software Engineering:

1. Specification
2. Methodical program development
3. Structuring of software systems
4. Re usability of Software components
5. Project Organization
6. Requirements for software development tools
7. Automatic generation of software
8. Quality Assurance
9. Documentation.

SQL GROUP BY AND HAVING CLAUSE WITH EXAMPLES

This is one of the important topic in SQL,we have discussed joins in SQL already. SQL includes many aggregate functions,which take information from multiple rows and aggregate it down to produce fewer rows in the final result set."It is used to group the results from one or more tables".

When to use Group By clause?

In fact, if you use select statement  the entire table records  formed as one group by group functions.When we need aggregations like below,we have to use Group by Clause:

• Department-wise total salary of employees
• Month-wise count of employees joined
• Account type and branch-wise average balance maintained

Syntax:

SELECT column_name,function(column_name)

from table_name

GROUP BY column_name

Here is i am taking employee table from them list out job designation_wise number of employees working and total salary from employee table

From the above employee table list out the  job designation_wise and total salary of employees.

Example:

SELECT job,count(*) no_of_employees,sum(sal) total_salary from Employee e

GROUP BY job;

Here job is the column by which rows of employees table are grouped

Result will be:

Having Clause:

The Having clause allows us to filter out groups that do not meet a specific requirement.It is used to mention condition in GROUP based SQL function like WHERE clause.

WHERE clause is executed on actual rows of the table being required.

Syntax:

SELECT column_name,function(column_name)

from table_name 

WHERE column_name condition

GROUP BY column_name

Having function(column_name)condition

Now, we will list out  from the above employee table  department wise no of employees and average salary,of those employees who do not get a commission and only for those departments in which employees get a at least a salary of 25000 or above.

Example:

SELECT Dept_no,count(*)no_of_employees,avg(sal)Avg_sal

from employees

where COM is NULL

GROUP BY Dept_no

Having Min(sal)>=20000

Order By Avg_sal DESC

TCL Commands in SQL

TCL stands for Transaction Control Language.Here transaction means a series of group of SQL statements that are logically related on Oracle table data is called as Transaction. It is used to control and manage transactions to maintain the integrity of data within SQL statements. When we changes the table data then to make those changes as permit we use COMMIT statement has to be given in SQL prompt.To do undo or a part of  the entire Transaction then we use ROLLBACK statement.

The fallowing are TCL statements:

1. COMMIT
2.ROLLBACK
3.SAVE POINT

1.COMMIT:
A COMMIT make changes done in transaction permanent. That means it ends the current transactions and makes permanent any changes made by the time transaction.

Syntax:
COMMIT;
Example:
insert into Student(SID,SName,SAdd) values(1001,'abc','bangalore');

COMMIT;

2. ROllBACK:
It restores the state of the database to the last commit point.That means it undoes any changes made during the transaction. 

Syntax:
ROLLBACK;

Example:

Delete from Student;
ROLLBACK;//it undo the changes

3. SAVEPOINT:

Whenever processing a transaction it specify a point in a transaction to which later you can rollback.An active SAVAPOINT is used to rollback partial transaction,as far as specified SAVEPOINT. 

Syntax:
SAVEPOINT  Savepointname;

Example:

insert into Student(SID,SName,SAdd) values(1001,'abc','bangalore');
SAVEPOINT x;

insert into Group(GID,GName,Status) values(101,'B.tech','pass');
SAVEPOINT y;

insert into Dept(DID,DName,location) values(1003,'HR','hyderabad');
SAVEPOINT z;

After inserting data into table,now  if you give ROLLBACK to x;

Then row from Dept table and Group table will be rollbacked.

TRUNCATE statement:
It is a Data Definition Language(DDL) statement rather than DML statement.It can not easily be undone.It is more efficient method of emptying a table by using the TRUNCATE
statement. This statement is use to quickly remove all rows from a table or cluster. We can remove rows from tables by using TRUNCATE statement very fast than with Delete statement for the fallowing Reasons:

1. TRUNCATE statement is a DDL statement and generates no rollback information.
2. DML requires many resources  to delete all rows that are inserted in the table.

Where Truncate can't be applied:

If the table is a parent of a referential Integrity constraint,you can not TRUNCATE the table,firstly you need to disable the constraint before issuing the truncate statement.

Syntax: TRUNCATE table Table_name;

Example: TRUNCATE table Student;

UML Tutorial

I am going to write a topic Unified Modelling Language(UML), it is a standard visual model language for writing software blueprints. The main goal of UML is to become a common language for creating models of Object Oriented computer software. This common language for business analysts,Software Architect and software developers mostly used to design,specify,describe and structure and behavior of artifact of software system.Use Case provides a way for your developers to come to common understanding with your system's end users and domain experts.Well structured use cases represents essential system or sub system behaviors.
Where can The UML be used?

The UML is intended primarily for software systems. It has been used effectively for such domains are:

• Enterprise information systems
• Banking and Financial Services
• Telecommunications
•  Retail
• Healthcare
• Scintific
• Distributed web-services

 The UML is not limited to modeling software,it is also used in nonsoftware system such as workflow in the legal system,the structure and behavior of a patient health care system and
hardware design.

Building Blocks of UML:

UML has three kinds of Blocks.They are
1.Things
2.Relationships
3.Diagrams
   

 

The present version of UML is UML 2.5 released in 2015 and the most useful standard diagrams are use case diagram,class diagram,sequence diagram,activity diagram, component diagram and deployment diagram. 

Why do we model?

There is one fundamental reason, we build models so that we can better understand the system that we are developing.
The fallowing aims can achieve through modeling:

1. Models help us to visualize the system as it is or as we want it to be.
2. Models permit us to specify the structure or behavior of the system.
3. Models give us a template that guides us in constructing system.    

Use Case diagram:

The main purpose of this diagram is to tell the developers about functional requirements of system including the relationship of actors  to essential process and different use cases. Here actors are called users,according to the UML notation actors might be person or hardware.Use Case deal only in the functional requirements of the system. 

The fallowing Use Case diagram show how system interacts with its environment,typically interactions involving its users. You can apply use cases to your whole system or to part of your system.

 In the above notation permits to visualize a use case apart from its realization and in context with other use cases. Here,graphically uses case is rendered as  in ellipse.

Class diagram:

The purpose of this class diagram is to depict the classes within a model. In an object oriented application, class have attributes(memeber variables) and operations(member functions) and relationship with other classes.The fundamental element of the class diagram is an icon the represents a class. The fallowing diagrams shows the class diagram.

A class is simply a rectanlge divided into three components. The topmost compartment contains name of the class.The middle one contains a list of attributes(member variables) and the bottom compartment contains a list of operations(member functions).

Example:
In this example i am taking name of the class is circle and their attributes,operations.

In the Next Sessions we will discuss remains diagrams.