SQL Alias

sql Alias is used to give an alias name to a column or a table. This is used for giving short name of a column and a table. you have to use alias, when column name is large or you can combine two column in a single column name or more readable.

SELECT * FROM Employee

 Aliases for columns:

SELECT

column-name as alias-name

from

table-name

Example1:

SELECT

  First_name AS [Employee Name]

FROM Employee

Result:

 

In the above query, the column First_name is given a alias as "Employee Name". So when the result is displayed the column name appears as "Employee Name" instead of  'First_name'.

Example2:

SELECT

  First_name + ' '+ Last_name AS [Employee Name]

FROM Employee

Result:

In the above query, the column First_name and Last_name combine together to display a single column as alias as "Employee Name". So when the result is displayed the column name appears as "Employee Name" instead of  "First_name" and "Last_Name". 

Table Name Alias

Syntax:

 

SELECT column-name

from table-name as alias-name

Example1:

Consider Two tables, First is Employee and Second is tblDepartment. 

SELECT

  emp.First_name, emp.Last_name,emp.Salary, emp.Joining_date, Department_ID

FROM Employee emp

 

SELECT dept.Id, dept.Name as [Department Name]

FROM tblDepartment dept

Below is the Query to fetch data from both the tables using SQL Alias,

 

SELECT 

  emp.First_name, emp.Last_name,emp.Salary, emp.Joining_date,

  dept.Name as [Department Name] 

from Employee as emp

INNER JOIN tblDepartment as dept

ON emp.Department_ID=dept.Id

 

Result

 

 

 

 

 

 

 

  

  

outlook doesn-t update emails unless you click send receive

The default setting for send/receive is 30 minutes. If someone send me mail and we are not received mail immediately means we have to make change in send/received settings 30 minutes to 2 minutes.

I am referring to the settings in Tools -> Options -> Mail Setup -> then look in the Send/Receive section.

Polymorphism in C-Sharp

1. In Polymorphism poly means “multiple” and morph means “forms” that means many forms.

2. In polymorphism we will declare methods with same name and different parameters in same class.

3. or methods with same name and same parameters in different classes.

In Polymorphism we have 2 different types those are

     -      Compile Time Polymorphism (Called as Early Binding or Overloading or static binding)

     -      Run Time Polymorphism (Called as Late Binding or Overriding or dynamic binding)

Compile Time Polymorphism or Early Binding

Compile time polymorphism means we will declare methods with same name but different signatures because of this we will perform different tasks with same method name. This compile time polymorphism also called as early binding or method overloading.

Method Overloading or compile time polymorphism means same method names with different signatures (different parameters)

Example

public class Class1 { public void NumbersAdd(int a, int b) { Console.WriteLine(a + b); } public void NumbersAdd(int a, int b, int c) { Console.WriteLine(a + b + c); } }

In above class we have two methods with same name but having different input parameters this is called method overloading or compile time polymorphism or early binding. 

Run Time Polymorphism or Late Binding

Run time polymorphism also called as late binding or method overriding or dynamic polymorphism.

Run time polymorphism or method overriding means same method names with same signatures.

In this run time polymorphism or method overriding we can override a method in base class by creating similar function in derived class this can be achieved by using inheritance principle and using “virtual & override” keywords.

Example

public class clsShape     {         public int _radius = 5;         public virtual double getArea()         {             return 0;         }     }     public class clsCircle : clsShape     {         public override double getArea()         {             return 3.14 * _radius * _radius;         }     }     public class clsSphere : clsShape     {         public override double getArea()         {             return 4 * 3.14 * _radius * _radius;         }     }

As you can see from above code that we have one base class "clsShape" with a "virtual" method "getArea()" and two derived classes "clsCircle" and "clsShape" each having an "override" method "getArea()" with different implementations.