https://blog.csdn.net/u013303551/article/details/52354230

SELECT t.table_name,
       t.colUMN_NAME,
       t.DATA_TYPE || '(' || t.DATA_LENGTH || ')',
       t1.COMMENTS
  FROM User_Tab_Cols t, User_Col_Comments t1
WHERE t.table_name = t1.table_name
    AND t.column_name = t1.column_name;