CREATE TRIGGER tr_ItemsPurchaseRestrictions ON UserGameItems FOR INSERT
AS
BEGIN

  DECLARE @userGameLevel int = (

    SELECT ug.Level

    FROM inserted AS ugi -- UserGameItems

    JOIN UsersGames AS ug ON ugi.UserGameId = ug.Id

  );

  DECLARE @itemMinLevel int = (

    SELECT i.MinLevel

    FROM inserted AS ugi -- UserGameItems

    JOIN Items AS i on i.Id = ugi.ItemId

  );

  IF(@itemMinLevel > @userGameLevel)

    BEGIN
      ROLLBACK;

      RAISERROR('Higher user game level required for item purchase', 16, 1);

      RETURN;

    END
END
--testing
INSERT INTO UserGameItems (ItemId, UserGameId) VALUES (3, 2);
INSERT INTO UserGameItems (ItemId, UserGameId) VALUES (3, 3);