I am using Oracle 11g for my web application. I want to add a column and a comment to an existing table. I can do that easily with the below commands
ALTER TABLE
No, you can't.
There's no reason why you would need to. This is a one-time operation and so takes only an additional second or two to actually type and execute.
If you're adding columns in your web application this is more indicative of a flaw in your data-model as you shouldn't need to be doing it.
In response to your comment that a comment is a column attribute; it may seem so but behind the scenes Oracle stores this as an attribute of an object.
SQL> desc sys.com$
Name Null? Type
----------------------------------------- -------- ----------------------------
OBJ# NOT NULL NUMBER
COL# NUMBER
COMMENT$ VARCHAR2(4000)
SQL>
The column is optional and sys.col$
does not contain comment information.
I assume, I have no knowledge, that this was done in order to only have one system of dealing with comments rather than multiple.