本篇文章为大家展示了表和列的comments的用法是什么，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

— Add comments to the table
comment on table EMP
  is 'Employee';

— Add comments to the columns
comment on column emp.mgr
  is 'Manager';

— Retrieving Table Comments
SELECT *
FROM user_tab_comments
WHERE table_name = 'EMP';

— Retrieving Column Comments
SELECT *
FROM user_col_comments
WHERE table_name = 'EMP';

— delete comments to table, only set the value null
comment on table EMP
  is '';

— delete comments to column, only set the value null
comment on column emp.mgr
  is '';