Query Table Name where specific column not exist in table.

SELECT    'ALTER TABLE '
       || table_name
       || ' ADD (
   SS_CREATOR      NUMBER(10) DEFAULT 1001 NOT NULL
  ,SS_CREATED_ON   DATE  DEFAULT SYSDATE NOT NULL
  ,SS_MODIFIER     NUMBER(10)
  ,SS_MODIFIED_ON  DATE);'
  FROM user_tables
 WHERE table_name NOT IN (SELECT DISTINCT table_name
                                     FROM user_tab_cols
                                    WHERE column_name = 'SS_CREATED_ON');