You could do it with 1 sql query if you just wanted every subject to be the exact same, ie: "Subject" and not "Re: Subject"
You'd need to know the first post number for the thread and then you could use the following SQL command:
UPDATE w3t_Posts SET B_Subject='New Subject' WHERE B_Main='ThreadNumber'
If you wanted the first post to be "Subject" and all the others to be "Re: Subject" it would take 2 sql commands:
UPDATE w3t_Posts SET B_Subject='Re: Subject' WHERE B_Main='ThreadNumber'
UPDATE w3t_Posts SET B_Subject='Subject' WHERE B_Main='ThreadNumber' AND B_Topic='1'
Make sure you do a db backup before trying either of these <img src="https://www.ubbcentral.com/boards/images/graemlins/wink.gif" alt="" />
