Help forming an SQL Query

[kronnos]

I had a few hundred subscribed members in primary usergroup but now want to change them all to secondary usergroup.

Basically, Im trying to form an sql query that would

1. Select all users with primary usergroup "A"
2. Then change that "A" to a "B" in the primary usergroup
3. Then add "A" to that users secondary group(some users have more then one secondary membership group)
4. And set the display group of all these users to "A"

A huge thanks in advance!