/*  UNION ALL  이용 샘플      
    FULL OUTER JOIN 이용하셔도 됩니다.
    CTAS 이용하시면 간단히 복사할수 있습니다.
*/
SELECT T.* 
   FROM  ( SELECT  COLUMN_NAME
                 , DATA_TYPE
                 , DATA_LENGTH
                 , DATA_PRECISION
                 , DATA_SCALE
              FROM USER_TAB_COLUMNS
             WHERE TABLE_NAME = 'A' 
        
             UNION ALL
        
            SELECT COLUMN_NAME
                 , DATA_TYPE
                 , DATA_LENGTH
                 , DATA_PRECISION
                 , DATA_SCALE
              FROM USER_TAB_COLUMNS
             WHERE TABLE_NAME = 'B' 
            ) T
   GROUP BY COLUMN_NAME , DATA_TYPE , DATA_LENGTH , DATA_PRECISION , DATA_SCALE
   HAVING COUNT(*) = 1