-- 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 '';

ITPub博客

表和列的说明(comments)的用法