Re: validate the uniqueness of data first before inserting
Re: validate the uniqueness of data first before inserting
- Subject: Re: validate the uniqueness of data first before inserting
- From: Ashley Aitken <email@hidden>
- Date: Wed, 16 Jun 2004 21:04:26 +0800
On 16/06/2004, at 8:43 PM, Patrick Robinson wrote:
On Jun 16, 2004, at 6:09 AM, Ashley Aitken wrote:
On 16/06/2004, at 5:32 PM, Goh Keng Boon wrote:
I got this field called customer_code which is keyin by user
manually and it need to be unique. How can it check if it is unique
first
before inserting the whole record into database?
Try and fetch an object/record with the same value for customer_code
...
The problem with this approach is that someone else could insert a row
with your customer_code value after you check for it, but before your
insert fires.
This is a case where it's nice when you can depend on the database to
enforce constraints... you can catch any resulting exceptions, and
handle appropriately.
Yes, that's true. Thus, if this was likely and would cause a
significant problem (ie it couldn't be easily fixed without
significance at a later time) then one could either lock the database
table between the before the fetch and until the row is saved, or as
you suggest perhaps use a database-specific constraint on a column .
Cheers,
Ashley.
--
Ashley Aitken
Perth, Western Australia
mrhatken at mac dot com
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