How to add comment on column of table or schema in oracle

How to add comment on column  of a table or schema in oracle 

Syntax:

 COMMENT ON  COLUMN table_name.column_name IS 'comment description';

For example,

 create table student(s_id number primary key,s_name varchar(20) not null );

After this if you want to comment of s_id column which acn be done as below:

  

 comment on column student.s_id   is  'abbreviation of student id';

You can remove comment by setting it to null as shown below:

  

 comment on column student.s_id   is ' ';

Add comment in Oracle sql