title: What does this MySQL query mean?
body: <p>I'm trying to understand some queries</p>
  <p>one of them is</p>
  <pre><code>(select (@a) 
   from (select(@a:=0x00)
       ,(select (@a) 
         from (information_schema.schemata)
         where (@a) in (@a:=concat(@a,schema_name,'&lt;br&gt;'))
         )
   ) a
  )
  </code></pre>
  <p>What does this query mean?</p>