Page 6 - DDL and DML Commands
P. 6

Removing Table Components

               Alter table Emp1
               Drop Primary Key, drop foreign key fk_1, drop column deptno;
               Alter table dept
               Drop primary key cascade;
               (The cascade option drops any foreign keys that reference the primary key.)

               Destroying Table
               Condition is table must be empty.
               If Exists – checks if the table exists
               Syntax is:
                       DROP TABLE [IF EXISTS]<table name>
               Example:
                       DROP TABLE IF EXISTS stream
               COMMIT command makes the changes permanent in a table.
   1   2   3   4   5   6