SET XACT_ABORT ON时，在事务中，若出现错误，系统即默认回滚事务，但只对非自定义错误有效
SET XACT_ABORT OFF，默认值，在事务中，回滚一个语句还是整个事务视错误的严重程序而定，用户级错误一般不会回滚整个事务
Q:you are writing a set of queries against a filestream-enabled database. you create a stored procedure that will update multiple tables within a transaction.you need to ensure that if the stored procedure raises a run-time error,the entire transaction is terminated and rolled back.which T-SQL statement should you include at the beginning of the stored procedure?
A:SET XACT_ABORT ON