Hi,
consider that have the following use case for my blog
comment and post have one to one relationship
A comment is drafted first and then linked to the post.
Only one comment is allowed per Post.
All comments appear in a grid to user can select one by clicking a radio button before actually creating a Post.
comments can be searched as they appear in the grid (like search but without delete, view and update buttons).
Please guide me. Thanks in anticipation.
I am not sure I got you. I guess you are talking about one comment per post per user.
Even if one post maximum per user is allowed, you still have a relation one to many (one post, many comments).
After that I don’t get your radio button story for selecting a comment and creating a Post… sorry 
We are not concerned about users. a one to one relation exist only between post and comment. i.e only one comment is allowed per post. i am just symbolising blog application with mine for easy understanding.
reg the UI, a list box with lot of fields from comments table (just for example) will limit users view to only one row but i want them to search the entire table both row wise and column wise before picking the required row, for establishing the link (between post and comment).