DDL Commands 
Create : used to create a table 
Alter : used to make changes on a table 
	- Add : used to add a column, constraint
	- Modify : to modify a column 
	- Drop : to delete a column, constraint or the whole table 

//The difference between varcher2 and char 

course_name varchar2(15)
---------------
itec212

course_name char(15)
itec212--------

//The difference between the number data types

85.65

midterm number(4) => 85--
midterm number(4,2) => 85.65

//Constraint types
primary key => pk
forgein key => fk
not null => nn
unique => uk
check => ck

//Create 

create table itec212        
(std_id number(8) constriant itec212_std_id_pk PRIMARY KEY,
 name varchar2(50) constraint itec212_name_nn NOT NULL,
 phone_no number(15),
 email varchar2(50) )

//Alter

//adding a new column to the table 

alter table itec212
add (midterm number(4,2))

//adding a constraint to a column 

alter table itec212
add constraint itec212_phone_no_uk UNIQUE(phone_no)

//Changing the size of a column

alter table itec212
modify (phone_no number(20))

//deleting a column 

alter table itec212
drop column email

//deleting a constraint from a column 

alter table itec212
drop constraint itec212_std_id_pk CASCADE

//deleting the whole table 

drop table itec212