Question

Is this possible?

I would like to have a limit for a user, lets say 5 databases.

So when he tries to issue a CREATE query to create a 6th an exception is thrown.

Answer 1

No, you cannot do this – at least not in a declarative way (just simply specify the max number of databases owned for each user).

The closest you could get with standard SQL Server functionality would be to create a DDL trigger for CREATE DATABASE and in that trigger, check to see if the current user already owns five databases, and in that case, let the trigger fail the operation.

Something along the lines of this (taken from TechNet sample):

CREATE TRIGGER ddl_trig_database 
ON ALL SERVER 
FOR CREATE_DATABASE 
AS 
    -- here, check to see if current user already owns five databases
    -- and if so, fail the trigger by using RAISERROR
GO