title: SQL - Unknown column in where clause
body: <p>I am rather new with <code>SQL</code> and I can't for the life of me figure out why I can't do what I'm trying here. I'm trying get the least number of free seats in a package-trip, and group them by the package ID. </p>
  
  <p>The first of the subqueries work, but the second is the one I can't figure out. It says   </p>
  
  <p><em>Unkown column SuperPaket in 'where clause'</em>.</p>
  
  <pre><code>select Paket.PaketID as "SuperPaket", Beskrivning, Resa.AvgångStad, Resa.AvgångTid, Resa.AvgångDatum,
  
      (select AnkomstTid from Resa where Resa.ResID in 
          (select ResID from PaketResa where PaketResa.PaketID = SuperPaket and Ordningsnr =
              (select max(Ordningsnr) from PaketResa where PaketResa.PaketID = SuperPaket))) "AnkomstTid",
  
          (select min(LedigaPlatser) from
              (select sum(AntalPlatser - Count) "LedigaPlatser", ResID from(
                  select Bokning.ResID, AntalPlatser, sum(Bokning.AntalBiljetter) as Count from 
                      (Resa inner join Bokning on Resa.ResID = Bokning.ResID) where Bokning.ResID in
                          (select PaketResa.ResID from PaketResa where PaketResa.PaketID = SuperPaket)
                  group by Bokning.ResID order by Count desc)
              as CountTable group by ResID) 
          as T) "LedigaPlatser"
  
      from ((Paket inner join PaketResa on Paket.PaketID = PaketResa.PaketID) inner join Resa on PaketResa.ResID = Resa.ResID) group by Paket.PaketID;
  </code></pre>
  
  <p>Why does this work for the first subquery but not the second one?</p>
  
  <hr>
  
  <p>Update..
  The error seems to appear when I put a "sub-subquery" in a from clause. I don't know how to rewrite the problematic query to fix this problem though, and I would really appreciate some help. Thanks..</p>