From: Jorgen Loland
Date: November 25 2010 12:51pm
Subject: Re: bzr commit into mysql-next-mr-bugfixing branch (tor.didriksen:3236)
 WL#1393
List-Archive: http://lists.mysql.com/commits/125024
Message-Id: <4CEE5BC9.9080004@oracle.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit

On 11/24/2010 04:36 PM, Tor Didriksen wrote:
> On 2010-11-19 12:59, Øystein Grøvlen wrote:
>> > +################
>> > +## Test with subqueries
>> > +SELECT d1.* FROM t1
>> > +LEFT JOIN (SELECT * FROM t1 LIMIT 30) d1 on t1.f1=d1.f1
>> > +ORDER BY d1.f2 DESC LIMIT 30;
>>
>> I do not think the result of the above query is well defined since the
>> contents of the derived table, d1, is not explicitly ordered.
>
> ???

Without ordering, "select * from t1 limit 30" will return the first 30 records 
it encounters, but the order depends on the access method. You then left join 
these 30 "random" records with t1. A different access method for t1 in the 
subquery may therefore change the result.

-- 
Jørgen Løland | Senior Software Engineer | +47 73842138
Oracle MySQL
Trondheim, Norway