SQL-Queries

create table Myset

(

name varchar(15),sal int,age int

)

insert into Myset values('e',5,50)

select*from Myset

select*from Myset order by sal desc

select*from Myset order by sal asc

select*from Myset where  sal not in (3,5)

select*from Myset where  sal in (3,5)

select*from Myset where  sal is  not null

select*from Myset where  sal between 2 and 5

select max(sal)from Myset

select min(sal)from Myset

select avg(sal)from Myset

select sum(sal)from Myset

select count(sal)from Myset

select max(sal)from Myset where sal<>(select max(sal) from Myset)

select sal,max(age)from Myset group by sal

select * from Stu_Table

where Stu_Name like '%k%'

SELECT * FROM Stu_Class_10

UNION ALL

SELECT * FROM Stu_Class_12

SELECT * FROM Stu_Class_10

UNION

SELECT * FROM Stu_Class_12

SELECT column_name(s)

FROM table_name1

right JOIN table_name2 

ON table_name1.column_name=table_name2.column_name

CREATE VIEW Stu_View( Stu_id, Stu_Name, Stu_Class)

AS SELECT  Stu_id, Stu_name, Stu_class

FROM Stu_Table

Select * from Stu_View

SELECT Stu_Id, Stu_Name, Stu_Class

FROM Stu_Table

where Stu_Id = 1 AND Stu_name = 'komal'

select * from Stu_Table

where stu_name like 'k%'AND stu_id = 1

select s.stu_id, s.stu_name, s.stu_class

from Stu_Table as s , Stu_Table as l

where s.stu_id = l.stu_id

static-a key word

Lets explain that what is static  in java.

if we make a class static then it means members of this class will be accessed directily by class name.and we can not create instanse of this class.

only static mamber can access to other static member.
 if any non-static member want to access any non-static member then it need to access throught the instance of that class

Custom Exception

Defining your own Exception class in JAVA
Now you know how to write exception handlers for those exception objects that are thrown by the runtime system, and thrown by a method in the standard class library.
It is also possible for you to define your own exception classes and to cause objects of those classes to be thrown whenever an exception occur. In this case, you get to decide just what constitutes an exceptional condition. For example, suppose you could write a data-processing application that processes integer data obtained via a TCP/IP link from another computer. If the specification for the program indicates that the integer value 100 should never be received, then you could use an occurrence of the integer value 100 to cause an exception object of your own design to be thrown.

 
Exception Types

Mainly Exceptions are of two types; checked and unchecked exceptions:

• Error and Runtime Exception are unchecked these exception not handled or check by compiler that you  handle them explicitly
• All other Exception are checked that is compiler enforce or check that you can handle them explicitly

An error is an abnormal situation of the JVM (Java Virtual Machine)

• Running out of memory
• Infinite recursion
• Inability to link

Creating Custom Exceptions

• Use the Exception class in the API.
• Create a Custom Exception class if  the predefined class is not sufficient.
• Declare a custom exception classes by extending the Exception class or  a subclass of Exception.

If you decide to define your own exception class. it must be a subclass of a Throwable class. You must decide which class you will extend.
The two existing subclasses of Throwable are Exception and Error.   Example-1 
This example is making your own Exception class by using constructor. 

// this is a user define exception class etend by Exception class
class Myexception extends Exception
     {
      public Myexception(int i)
        {
        System.out.println("you " +i +" entered It exceeding the limit");
        }

      }

public class ExceptionTest
    {
    public void show(int i) throws Myexception
          {
       if(i>100)
         throw new Myexception(i);
       else
         System.out.println(+i+" is less then 100 it is ok");
          }

   public static void main(String []args)
        {
        int i=Integer.parseInt(args[0]);
        int j=Integer.parseInt(args[1]);
        ExceptionTest t=new ExceptionTest();
            try{
                t.show(i);
                t.show(j);
                }
                catch(Throwable e)
                        {
                System.out.println("catched exception is"+e);
                        }
        }
}
OUTPUT

Example-2
This example is making your own Exception class by using super keyword.
class MyException extends Exception
    {
    MyException(String s)
     {
      super(s);
     }
    public String toString()
        {
           return(" " + getMessage());
        }
   }class ThrowClass  {
    int age;
     ThrowClass(int age)  throws MyException
       {
       this.age=age;
       }        
     void getAge(int age) throws MyException
      {
       if(age <18 )
        {
         throw new MyException("Invalid Age");
              }
        else
        {
         this.age=age;
        }
      }
   }
   class TestException   {

    public static void main(String [] args)
     {
        int a=Integer.parseInt(args[0]);
       try        {
          ThrowClass t=new ThrowClass(a);
            t.getAge(a);
       System.out.println(t.age);
        }
        catch(MyException me)
           {
          System.out.println(me);
              }
     }
   }

OUTPUT