Ever deleted some tables accidently and had to waste your time doing them all over again? Oracle, in conjunciton with Triggers, provides an easy solution to this problem.

First, create a table that holds the table name. Say you create a table called SafeTable with a column names SafeTableName and the datatype varchar2. Populate this table with the table names that should not be dropped. Then go ahead and create the trigger as follows:

CREATE or REPLACE TRIGGER checkForSafeTable BEFORE DROP ON DATABASEDECLARE  TABLENAME CHAR(20);BEGIN  SELECT SafeTableName INOT TABLENAME from SafeTable   WHERE UPPER(TABLENAME)=ora_dict_obj_name;  IF sql%found THEN    RAISE_APPLICATION_ERROR(-20001,'This is a SAFE table');  END IF;EXCEPTION  WHEN no_data_found   THEN dbms_output.put_line('This table will be dropped');END;

When you create this trigger, you cannot drop any table that has an entry in the SafeTable.