Differentiate between system generated constraint naming and user generated constraint nameing.

The difference between system generated constraint naming and user generated constraint naming are as follows: There are two level of constraint naming:

• System generated system naming
• user defined system naming

Also there are two levels of defining constraint naming. They are:

• column level 
• table level

1. System generated, column level constraint 

   CREATE TABLE tbl_student_info (
   
   student_id_number primary key,
   FName varchar(25) NOT NULL,
   MName varchar(25),
   LName varchar(25) NOT NULL,
   Gender char(1) check (Gender IN('M','F','m','f')),
   DOB date NOT NULL,
   Email varchar (50) check (Email like '%@@'));
    example, 

          insert into tbl_student values(1,'Ram','bahadur','Karki','M','07/12/2012','ramg@gmal.com');

1. User defined with column level and table level defining constraints  

   CREATE TABLE course_info(
   
   course_id number constraint  course_info_course_id_pk primary key,
   MdName varchar(25) constraint course_info_MdName_nn NOT NULL,
   MdCredit number constraint course_info_MdCredit_nn NOT NULL,
   SsPeriod char(6) constraint course_info_SsPeriod_nn NOT NULL,
   constraint course_info_MdCredit_c check (MdCredit>=3),
   constraint course_info_SsPeriod_c check(SsPeriod IN ('SPRING','AUTUMN'))
   );
   
   Advantage of using user defined constraint
   When the database structure is large and contains huge amount of data, it helps in performance tuning.