Is a stored procedure in a database system is a call back mechanism?

Is a stored procedure in开发者_如何学运维 a database system is a call back mechanism ?

Not sure I really get the question. Do you mean:

Is a stored procedure in a database system in itself a call back mechanism?

Or

Do stored procedures have a call back mechanism?

In the first instance, the answer is no, but for me, that question doesn't make much sense.

In the second instance, again the answer is no, if you are wanting a formal dedicated callback machanism. However, a form of callback can be achieved using dynamic SQL and stored procedure parameters.

Consider the following

CREATE Procedure usp_test (@callback varchar(100))
AS
EXEC (@callback)

Here, we are passing the name of the procedure in a string and executing as dynamic SQL. We can, of course append parameters to it if we want. It isn't a tryue callback as we are not passing a reference.

In all honesty, however, it sounds like you don't understand the question. Maybe a better question would have been to enquire as to the meaning of the question?

Databases are basically passive. No calls = no action.

When a database emails you, it is in fact some scheduled client code that calls the database and sends the email.

"A happy database has no users" of course