> Unique and random are somewhat orthagonal concepts. In order to
> enforce the uniqueness, you're placing a constraint on the random
> values, so they're not really totally random. For the random part,
> #randRange(0, 999999)# will take care of it. For the uniqueness,
> you'll have to check the generated value against all others in the
> database, and if the value is already in there, generate another
> random value. Repeat until you find one that is unique.
It's also important that you place a lock around the uniqueness test for
each individual number and that you numberformat(number,000000) if you
want to make sure the values are all 6 characters in length. So once
you've generated your random number with
rn = NumberFormat(RandRange(0,999999),000000);
Then you'll want to make sure you use a cftransaction around the test &
insert, i.e.
<cftransaction isolation="serializable">
<cfquery name="checkunique" ...>select x from mytable...</cfquery>
<cfif checkunique.recordcount eq 0>
<cfquery ...>insert into mytable ...</cfquery>
<cfelse>
<!--- here it's got to loop out of the transaction
to create another random number --->
</cfif>
</cftransaction>
Without that transaction then you have the associated risks of a race
condition.
--
s. isaac dealey ^ new epoch
isn't it time for a change?
ph: 503.236.3691
http://onTap.riaforge.org/blog
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