title: Problem with table JOIN in MySQL and aggregation
body: <p>I have three tables. This query will write down the right answer (x-lines for btv.id_user with appropriate btv.cas and race.id_zavod</p>
  
  <pre><code>SELECT `btv.id_user`, `btv.id_zavod`,`btv.cas`
  FROM `btv`
  JOIN `btu` ON `btv.id_user` = `btu.id_user`
  JOIN `race` ON 'btv.id_zavod' = `race.id_zavod`
  WHERE `race.type` = '8' AND `btv.id_user` = '607'
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>| 607 |  512 | 03:15:58 |  
  | 607 |  730 | 03:01:18 |  
  | 607 |  164 | 03:07:26 |  
  | 607 |  767 | 02:58:31 |  
  | 607 | 1147 | 03:06:47 |  
  | 607 | 1149 | 03:09:41 |  
  | 607 | 1178 | 03:24:20 | 
  </code></pre>
  
  <p>But when I try to aggregate it to one row by the id_user it return correct min btv.cas but wrong join wrong race.id_zavod</p>
  
  <pre><code>SELECT `btv.id_user`, `btv.id_zavod`, MIN( `btv.cas` )
  FROM `btv`
  JOIN `btu` ON `btv.id_user` = `btu.id_user`
  JOIN `race` ON 'btv.id_zavod' = `race.id_zavod`
  WHERE `race.type` = '8' AND `btv.id_user` = '607'
  GROUP BY `btv.id_user`
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>| 607 | 512 | 02:58:31 |
  </code></pre>