Here[ refixed coder ], we will learn alter commands step by step with an oracle application. alter command to use add, edit, modify, rename and many more purpose. So, step by step we will discuss about alter :

CREATE TABLE:

CREATE TABLE EMPLOYEE(id INT,

    name VARCHAR(10));


ADD COLUMN:
ALTER TABLE EMPLOYEE ADD address VARCHAR(10);
DELETE COLUMN:
ALTER TABLE EMPLOYEE DROP COLUMN address;




MODIFY COLUMN:

ALTER TABLE EMPLOYEE MODIFY id VARCHAR(30);



CHANGE COLUMN NAME:
ALTER TABLE EMPLOYEE RENAME COLUMN id to reg_no;

CHANGE TABLE NAME:
ALTER TABLE EMPLOYEE RENAME TO EMP1;


MODIFY NORMAL COLUMN TO
PRIMARY COLUMN:
ALTER TABLE EMP1 ADD PRIMARY KEY (reg_no);