菲力貓的程式設計

Adding column to a table :
    ALTER TABLE table_name
     ADD column_name column-definition;

For example:
    ALTER TABLE supplier
     ADD supplier_name  varchar2(50);

Drop an Index :

    DROP INDEX index_name;

Drop a Primary Key :
    ALTER TABLE table_name
    drop CONSTRAINT constraint_name;

Disable a Primary Key :
    ALTER TABLE table_name
    disable CONSTRAINT constraint_name;

Enable a Primary Key :
    ALTER TABLE table_name
    enable CONSTRAINT constraint_name;