Hello Ian,
How are you ?
Yes, I don't have much experience with DB, but my DB is very very old, there are a lot of fields with differents properties and fields that they not existing anymore according in the new DB.
I think that my DB was from 2007 , it is very old !
The idea was update these fields and proporties, and I had some difficult because of the PK and FK.
Then, I researched a lot, for some months, and I learned a little bit more about DB and in fact, it is possible to do, but as you said, must have take care and I recommend to take a backup before to fix it or work in your DB. See the links that I used.
I've made a lot of backups, because I have many datas, users, foruns, topics, private messages, polls, etc. It were many tests before to go in production DB, but I got to fix, I updated ALL tables, including the tblThread, I removed the old fields, but before I certified that didn't have any datas there, I altered the properties, like NVARCHAR, Smallint, nText, sizes and lenght, etc .... well , it was a success, now my DB is with ALL corrections and the PK and FK again !!
As Bruce told in other post, some properties are similar and don't take any problem, but I would like to be with all corrected.
Maybe, there are others ways easier to fix it , but as I said, I don't have much experience and these articles that I found were the enough to fix my issue. If you know how, could you share with us.
If someone has with the same issue, will can be try using this tips, but don't forget to take a backup before, because if don't have a success it is only to restore the DB again.
Thank you for your concern.
Hugs.