Altering a Table

Finally, you should know that it is possible to "alter" a table after it has been created using either a standard GUI tool or by using the ALTER SQL command as follows:

ALTER TABLE  TABLE_NAME
      DROP   COLUMN_NAME, COLUMN_NAME
      ADD    COLUMN_NAME DATA_TYPE, COLUMN_NAME DATA_TYPE
      RENAME COLUMN_NAME NEW NAME
      MODIFY COLUMN_NAME DATA_TYPE;

such as the following case in which we alter the table named EMPLOYEES by dropping the E_GENDER Column and adding an E_ZIP column which will accept INTEGERS and which must be filled in for every new employee added to the table, and the E_MIDDLE_INIT column which will accept a single character as a value.

ALTER TABLE EMPLOYEES 
      DROP  E_GENDER
      ADD   E_ZIP INTEGER NOT NULL, 
            E_MIDDLE_INIT CHAR (1); 

Deleting Databases and Dropping Tables and Views
Introduction to Databases for the Web | Table of Contents
Introduction to Databases for the Web