How to edit urls of old posts

[Saeed Fazlollahzadeh]

Hi, all of external links of my forum have got nofollow attribute and there are lots of posts.
There are some old posts that I want them get follow attribute.
For example, there are two posts. The first one was made 2 years ago in which there exists vbulletin.com url, and another is made yesterday having vbulletin.com url.
I want just the first post's (2 years ago) url changes to follow.
I've observed posts table and there was bbcodes (no html codes) that had no nofollow or any html attribute to edit.
Should I ask at vbulletin.org ? Requires any important modification?
Thanks in advance

[Saeed Fazlollahzadeh]

"postparsed" table is the one to be modified.
Figured it out
Solved

[Mark.B]

We don't recommend editing the database directly.

You may break your site, and if you do there is no way back other than restoring from backup.

[Saeed Fazlollahzadeh]

Thanks Mark. I know what I'm doing