Use a specific database depending on the state

Question

Is there any way to use a specific database based on a certain condition? To clarify, I will give a naive example:

CASE 
    WHEN @dbnum = 1 THEN USE Db1
        ELSE USE DefaultDb
END

Answer 1

You can do this with IF:

IF @dbnum = 1
    USE Db1;
ELSE
    USE DefaultDb;