Maybe it is the tiny extra time to parse the unnecessary " LIMIT 1"? 

> -----Original Message-----
> From: Robert DiFalco [mailto:[EMAIL PROTECTED] 
> Sent: Tuesday, August 29, 2006 10:09 AM
> To: mysql@lists.mysql.com; [EMAIL PROTECTED]
> Subject: RE: Performance: LIMIT 1 with UPDATE
> 
> FWIW, my preliminary testing shows no performance increase for adding
> LIMIT 1 to the following construct:
> 
>       [ SELECT | UPDATE ]
>       WHERE Table.UniqueID = <N>
> 
> In fact, there seems to be a slight performance edge to NOT appending
> LIMIT 1 to the statement.
> 
> R.
> 
> -----Original Message-----
> From: Robert DiFalco [mailto:[EMAIL PROTECTED] 
> Sent: Tuesday, August 29, 2006 9:06 AM
> To: mysql@lists.mysql.com
> Subject: Performance: LIMIT 1 with UPDATE
> 
> Does using LIMIT 1 with UPDATE provide a performance improvement when
> the WHERE condition is on a unique index or primary key?
> 
> R.
> 
> 
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