Re: LAST_INSERT_ID and CRC32

Well, I think an update after insert is the only way. Other than
perpopulating another table with possibe crc values then usinga join:
Select id from testtable
Inner join crctable on testtable.id=3Dcrctable.id
Where crctable.crcval=3D'xxxxxxx'
Just be sure to index the crcval column.
On Sunday, May 3, 2009, thunder@isfahan.at wrote:
> Hi Johnny,
>
> I need the CRC32 for a unique URL-ID...
>
> I think it isn't to slow when I make a SELECT later in this form:
>
> Rows in Table: 825,984
>
> Search for id: 2532552 (CRC32: 46316330)
>
> SELECT id FROM `testtable` WHERE id =3D "2532552"
> 0.0005 sec.
>
> SELECT id FROM `testtable` WHERE CRC32(id) =3D "46316330"
> 0.5712 sec.
>
> OK, I can make an UPDATE after an INSERT but then I can't use UNIQUE for =
the Coloumn with the CRC32...
> Before I can make an Update, the Value is 0...
>
>
>
> I don't think its possible to do what you want in a single statement. Sin=
ce
> LAST_INSERT_ID() is set to the last insert id of the connection... and th=
e
> row you are inserting doesn't exist.. well.. until you create it, it will
> always either be zero or the record BEFORE your next insert, ie:
>
> INSERT INTO testtable(NULL,LAST_INSERT_ID());
> INSERT INTO testtable(NULL,LAST_INSERT_ID());
>
> would produce
> ID =A0 =A0CRC32ID
> 1 =A0 =A0 =A0 0
> 2 =A0 =A0 =A0 1
>
> You could run an update immediately after the insert to set the CRC32
> column:
>
> UPDATE testtable SET id-crc=3DCRC32(LAST_INSERT_ID()) WHERE
> id=3DLAST_INSERT_ID();
>
> Not quite sure why you need the CRC32 value of the ID, will it not always=
be
> the same value for the given ID number? Wouldn't it be easier to do it on
> the select side of the equation?
>
> SELECT id,CRC32(id) AS id-crc... FROM testtable...
>
> -jw
> On Sun, May 3, 2009 at 7:16 AM, thunder@isfahan.at wr=
ote:
>
>
>
> Hello,
> I have a questions and I hope, that is possible in MySQL.
>
> I have the following short Table.
> CREATE TABLE IF NOT EXISTS `testtable` (
> =A0`id` bigint(20) unsigned NOT NULL auto_increment,
> =A0`id-crc` bigint(20) unsigned NOT NULL,
> =A0PRIMARY KEY =A0(`id`),
> =A0UNIQUE KEY `id-crc` (`id-crc`)
> ) ENGINE=3DMyISAM =A0DEFAULT CHARSET=3Dlatin1 AUTO_INCREMENT=3D1 ;
>
>
> `id` is the unique autoincrement
>
> in `id-crc` I would like save the CRC32 from `id` (the coloumn is unique)
>
> E.G.
>
> id =A0 =A0 =A0id-crc
> --------------------
> 1 =A0 =A0 =A0 2212294583 =A0 =A0 =A0--> CRC32('1')
> 2 =A0 =A0 =A0 450215437 =A0 =A0 =A0 --> CRC32('2')
> 3 =A0 =A0 =A0 1842515611 =A0 =A0 =A0--> CRC32('3')
>
> I would like insert the CRC32 directly when I make a new Insert. E.G.
>
> INSERT INTO `db283796092`.`testtable` (
> `id` , `id-crc`
> )
> VALUES (
> NULL , LAST_INSERT_ID()
> );
>
> But LAST_INSERT_ID() is 0!!!! How can I make that, that he use the actual
> INSERT-ID?
>
> Best regards
>
> Thunder
>
>
>
>
>
>
>
>
>
>
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--=20
-----------------------------
Johnny Withers
601.209.4985
johnny@pixelated.net
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