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From:Johnny Withers Date:February 22 2012 3:43pm
Subject:Re: Removing Data Duplicacy
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I'm not sure, It seems to me the proper way to do would be to insert into
table1, get the insert ID, then insert into table2 using that ID, this is
pretty standard stuff.

Not sure why, in this case, he cannot do that.

-JW


On Wed, Feb 22, 2012 at 8:54 AM, Rhino <rhino1@stripped> wrote:

> I miised the first message in this thread but is there some compelling
> reason why you simply don't use a unique index on the primary key of the
> table to prevent duplicates in the first place?
>
> --
> Rhino
>
>
> On 2012-02-22 09:40, Johnny Withers wrote:
>
>> You can also handle this with transactions:
>>
>> CREATE TABLE `seq` (
>>   `seq_num` int(10) unsigned NOT NULL DEFAULT '1000'
>> ) ENGINE=InnoDB DEFAULT CHARSET=latin1
>>
>>
>> #Initialize sequence numbers
>> INSERT INTO seq(seq_num) VALUES(1000);
>>
>> #Get next sequence number
>> START TRANSACTION;
>>
>> UPDATE seq SET seq_num=LAST_INSERT_ID(seq_**num+1);
>>
>> #Do other inserts into other tables with this sequence number
>>
>> COMMIT;
>>
>> #ROLLBACK if something fails
>>
>> Other inserts will be blocked until this process is either COMMIT'd or
>> ROLLBACK'd, preventing you from using the same sequence # again. As soon
>> as
>> the COMMIT or ROLLBACK occurs, the other transactions will continue.
>>
>> -JW
>>
>> On Wed, Feb 22, 2012 at 7:57 AM, Arthur Fuller<fuller.artful@stripped**
>> >wrote:
>>
>>  I agree with the testicular remedy, but in the case of the iron
>>> codpiece, I
>>> can think of another approach which may work for you. It still uses
>>> Select,
>>> but reads a one-row table, so it shouldn't hurt performance much. The
>>> table
>>> serves no other purpose than storing the next available PK; call the
>>> table
>>> NextPK, say. The algorithm might go like this:
>>>
>>> 1. Lock the table NextPK.
>>> 2. Select its value.
>>> 3. Update the column with current value + 1.
>>> 4. Unlock the table.
>>> 5. Do your inserts.
>>>
>>> The lock will be very brief, perhaps brief enough to satisfy your
>>> requirement.
>>>
>>> --
>>> Arthur
>>> Cell: 647.710.1314
>>>
>>> Only two businesses refer to their clientele as users: drug dealing and
>>> software development.
>>>
>>> -- Arthur Fuller
>>>
>>>
>>
>>


-- 
-----------------------------
Johnny Withers
601.209.4985
johnny@stripped

Thread
Removing Data DuplicacyAdarsh Sharma22 Feb
  • Re: Removing Data DuplicacyJohan De Meersman22 Feb
    • Re: Removing Data DuplicacyArthur Fuller22 Feb
      • Re: Removing Data DuplicacyJohnny Withers22 Feb
      • Re: Removing Data DuplicacyAdarsh Sharma23 Feb
        • Re: Removing Data DuplicacyJohan De Meersman23 Feb
Re: Removing Data DuplicacyJohnny Withers22 Feb
  • Re: Removing Data DuplicacyJohan De Meersman22 Feb