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Simpson, Ken wrote:
> Mark,
>
> <snip>
>
>>I'm using InnoDB tables, which are reputed to be ACID compliant.
>>Same problem.
>>
>>I guess I will follow your suggestion and just drop the UNIQUE
>>constraint since it appears to be evaluated after each row is
>>UPDATEd and not after the UPDATE completes.
>>
>>I'll check out how Postgres and Firebird handle this.
>>(Anyone want to try it on Oracle for me?)
>>
>>Regards,
>>Mark
>>[EMAIL PROTECTED]
>>
>
>
> This is Oracle's take on your issue:
>
[snip]
After talking with our resident SQL standards person, I've found out
that the SQL standard states that constraint checking must happen at the
end of statement completion (or deferred to transaction commit, if so
declared in the constraint definition).
Because MyISAM tables are not transactional, MySQL _can't_ defer
constraint checking to end-of-statement, because if a constraint was
violated during the processing of the statement, there would be nothing
to roll-back to. Therefore, MySQL has to perform constraint checks at
row-update time. This behavior is the same across all table types,
transactional or not, for consitencies' sake.
-Mark
- --
For technical support contracts, visit https://order.mysql.com/?ref=mmma
__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Mark Matthews <[EMAIL PROTECTED]>
/ /|_/ / // /\ \/ /_/ / /__ MySQL AB, SW Dev. Manager - J2EE/Windows
/_/ /_/\_, /___/\___\_\___/ Flossmoor (Chicago), IL USA
<___/ www.mysql.com
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