Oracle Tablename/Columns comments

1.  get all table comments

SELECT TABLE_NAME
      ,COMMENTS
FROM   USER_TAB_COMMENTS

2.  get sql for tables comments
SELECT 'COMMENT ON TABLE ' || TABLE_NAME || ' IS ''' || COMMENTS  ||  ''';' AS SQL
FROM   USER_TAB_COMMENTS

3. get sql for columns comments 
SELECT T.TABLE_NAME,
       C.COLUMN_NAME
      ,C.COMMENTS 
      ,  'COMMENT ON COLUMN ' || T.TABLE_NAME ||  '.' ||  C.COLUMN_NAME || ' IS ''' || C.COMMENTS  ||  ''';' AS SQL
FROM   USER_TAB_COMMENTS T, USER_COL_COMMENTS C
where T.TABLE_NAME = C.TABLE_NAME