I have the below trigger:
CREATE Trigger enroll_limit on Enrollments
Instead of Insert
As
Declare @Count int
Declare @Capacity int
Select @Count = COUNT(*)
If you are trying this from SQL Server Management Studio, here is another option which worked for me:
In the left pane, right-click on the database and select "New Query".
This connects you to the specific database. Now you can enter your create trigger statement as the first statement in the query window which opens. There is no need for a "use" command.