Not updating access query for null
Such draconian forms of concurrency control are referred to as pessimistic concurrency control.With pessimistic concurrency control there needs to be some mechanism where a user can lock a particular row or an entire database table and say, essentially, "No one can modify these records until I'm done!If you complete your purchase process by the deadline, the seat is yours.If you fail to complete the purchase by then - either because you go out to lunch or are just too slow in entering your information - the seat is "unlocked" and returned to the general pool. NET does not offer any built-in support for pessimistic concurrency control.If you need to implement this type of concurrency control you're on your own.Pessimistic concurrency control is useful in scenarios where concurrency violations absolutely, positively must not occur.If you are ordering a ticket to a concert or plane flight online, it's important that from the time you pick your seat to the time you place your order and provide your payment information that some other user doesn't sneak in and take the seat you're ordering.
He clicks the Edit button and starts to make his change. Will "Scott's Tea" be: The way the Sql Data Source control and Grid View work by default is to update all editable fields, regardless of whether they've been modified by the user or not.
NET 2.0 introduced a number of new Web controls designed for accessing and modifying data.
These controls allow page developers to declaratively access and modify data without writing any code to perform the data access. ) Because multiple users can visit the same web page concurrently, it is possible for a user visiting a data modification page to inadvertently overwrite the modifications made by another user. If two users visit this page simultaneously from different computers and both edit the same row, whomever saves the first will have her changes overwritten by whomever saves the row last.
Optimistic assumes that concurrency violations are rare and that if such an error occurs that it's adequate to ask one of the conflicting parties to re-enter their information.
Pessimistic concurrency, on the other hand, implements policies to ensure that concurrency violations cannot occur.