DATA TYPES IN ORACLE

1.Number(size): 
This Data type allows integer values such as student Roll No.'s,Employee No.'s etc.,                             Maximum Size of this Data Type is 1 to 38 digits.
2.Number(P,S): 
 This Data Type allows decimal values such as student Average Marks,Employee Salaries etc.,            Here P means Precision and S means Scale  
                          
Example:Salary=9870.67   NUMBER(6,2)                                            

* In this Total Number of Digits Including Decimal Places are  6 ,these 6 is Precision Value                  * Number of digits places are2 ,these 2 is Scale Value.
3.Alphabets: 
This Data Type allows to enter character values such as Student  Names,Employee Names etc.,      This Data Type further divided into following Types                       
        1)Char(size)                       
        2)Varchar2(size)

Char(size):This Data Type allows to enter Character Values employee Names,Student Names etc.,The Maximum Size of this data type is 1 to 2000 Characters. It always allocates some memory in a Static Fashion. 
Varchar2(size): This Data Type allows to enter character values such as Employee Names,Student Names, etc., The Maximum Size is 1 to 4000 Characters. It always allocates memory in a Dynamic Fashion.

4.Date: 
This Data Type allows us to enter date values such as Student joining date,employee hiredate  etc.,             The Default Format of Date Type is DD-MON-YY.             
        The Range of this Date Data Type is 01-jan-4712 BC to 31-DEC-999AD

5.TimeStamp: This Data Type allows us to enter both DATE & TIME.                        
                        The Default Format of TimeStamp is DD-MON-YY HH:MI:SS