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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.php
Subject: Re: Problem creating a series of tables
Date: Thu, 02 Apr 2015 22:32:33 +0200
Organization: PointedEars Software (PES)
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Jerry Stuckle wrote:

> On 4/2/2015 8:50 AM, the pedantic troll Thomas 'Pointed Head' Lahn wrote:
>> Denis McMahon wrote:
>>> Remember that if you don't specify a sort order in the mysql query, the
>>> ordering of the records it returns is random.
>> 
>> Incorrect.  The ordering is undefined if the table has no keys that
>> define
>> sort order.  For example, for a InnoDb table named `test` that has
>> 
>> | Field   Type    Null    Key     Default Extra
>> | id      int(10) unsigned        NO      PRI     NULL    auto_increment
>> 
>> the result of the MySQL query
>> 
>> | SELECT * FROM `test` LIMIT 1
>> 
>> will be the record with the smallest `id` field value.
>> 
>> $ php -v
>> PHP 5.6.7-1 (cli) (built: Mar 24 2015 12:30:15)
>> Copyright (c) 1997-2015 The PHP Group
>> Zend Engine v2.6.0, Copyright (c) 1998-2015 Zend Technologies
>>     with Zend OPcache v7.0.4-dev, Copyright (c) 1999-2015, by Zend
>> Technologies
>>     with Xdebug v2.2.6, Copyright (c) 2002-2014, by Derick Rethans
>> 
>> $ mysql -V
>> mysql  Ver 14.14 Distrib 5.5.42, for debian-linux-gnu (x86_64) using
>> readline 6.3
> 
> Incorrect (again).  It will return the first row in the table - which
> may or may not be the one with the smallest 'id' value.

Si tacuisses, philosophus mansisses.

,----
| mysql> create temporary table tmp (id int(10) primary key not null);
| Query OK, 0 rows affected (0.01 sec)
| 
| mysql> explain tmp;
| +-------+---------+------+-----+---------+-------+
| | Field | Type    | Null | Key | Default | Extra |
| +-------+---------+------+-----+---------+-------+
| | id    | int(10) | NO   | PRI | NULL    |       |
| +-------+---------+------+-----+---------+-------+
| 1 row in set (0.01 sec)
| 
| mysql> insert into tmp values (1);
| Query OK, 1 row affected (0.00 sec)
| 
| mysql> insert into tmp values (0);
| Query OK, 1 row affected (0.01 sec)
| 
| mysql> select * from tmp;
| +----+
| | id |
| +----+
| |  0 |
| |  1 |
| +----+
| 2 rows in set (0.00 sec)
`----

> By definition, order is undefined in a SQL database unless the ORDER BY
> clause is specified.

So much for theory – for which you want to cite evidence.

-- 
PointedEars
Zend Certified PHP Engineer
Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.