Hi Andrew,

I agree to Bruce's suggestion here. Actually making the two operation(query
existing name from db table  and insert new record with the name to db
table) in a transaction will only make the two operation set atomic, but
you will still encounter concurrent inserting issue that cause the
duplicated inserting error at inserting time.  Also I have discussed with
other DB engineers and this scenario is not quite suitable to implement at
DB level(through transaction or explicit locking , no record to lock).

I think you can consider the following approachs to prevent duplicated
inserting in application code layer:

**Making the data accessing class (do the query and insert) methods a
contral entry point in your application. Thus, you can perform explicit
lock/exclusive against the methods calls. This will hit concurrent
processing performance but is acceptable if there won't frequent occur such
read/inserting operations in your application.

** Add a global inserting id/name list(a limited queue) in your
application, this list will contains all the current/recent item name being
inserted(in sequence). Thus, when you perform inserting, you will need to
check both the DB and this list to see whether there're duplicated existing
record or any one being inserted now.

How do you think?

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead



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