I have two tables:  

One is for active users and the other one is for inactive users. Both have full name of the user and his email address.
I want to be able to insert a new user only if he doesn't exist (his email address for instance) in both tables.
If he exists in the inactive table I will reactivate him by just moving the user from the inactive table to the active table.

Is there a way doing that by just trying to insert with some kind of query and catching exception if he exists, and not by checking if the user exists before inserting?