SQL Triggers not preventing insert I am having trouble getting a trigger to work. What it needs to do is to prevent any customer with last name Glass from being inserted into the database. This is what I have:

CREATE TRIGGER no_last_name_glass_trg
ON customer
AFTER INSERT,UPDATE
AS
BEGIN
DECLARE @CUSTOMER_LAST VARCHAR;
SET @CUSTOMER_LAST= (SELECT INSERTED.customer_last FROM INSERTED);

  IF @CUSTOMER_LAST = 'Glass'
    BEGIN
    ROLLBACK
    RAISERROR('Applicant Glass Denied',14,1);
  END;
END;


The issue is when I add customers with last name of Glass, it inserts without throwing an error. Any ideas? I can make it work in Oracle, but the same method does not work in MS SQL.
The problem with your code is that you are declaring your variable as varchar without any length. With variable declarations, varchar defaults to a length of 1 (note that in other scenarios it will have a different default length).

As a best practice, you should always specify a length on the varchar datatype. For more details, see this article on the issue.