SQL Verschachtelung-Verständnisfrage

[Sandra]

Ich habe den Query jetzt folgendermaßen zusammengesetzt:
SELECT Country.Name,Country.Capital,City.Population,
  (SELECT SUM(Umland.Summe)
   FROM (SELECT City.Population Summe
         FROM City, Country C1
         WHERE City.Country=C1.Code AND City.Name !=C1.Capital
          AND City.longitude - (SELECT City.longitude
            FROM City, Country
            WHERE City.Name=Country.Capital AND City.Country=Country.Code AND C1.Code=Country.Code
            ) <= 0.1
           AND City.longitude - (SELECT City.longitude
            FROM City, Country
            WHERE City.Name=Country.Capital AND City.Country=Country.Code AND C1.Code=Country.Code
            ) >= -0.1
    AND City.latitude - (SELECT City.latitude
     FROM City, Country
     WHERE City.Name=Country.Capital AND City.Country=Country.Code AND C1.Code=Country.Code
     ) >= -0.1
    AND City.latitude - (SELECT City.latitude
     FROM City, Country
     WHERE City.Name=Country.Capital AND City.Country=Country.Code AND C1.Code=Country.Code
    ) >= -0.1)  Umland
      )
FROM City,Country
WHERE City.Name=Country.Capital AND City.Country = Country.Code

Leider wird die Summe pro Stadt noch nicht richtig berechnet. (Siehe bei http://dbpraktikum.ifi.informatik.uni-goettingen.de/sql.php)
Kann mir jemand sagen, welcher Fehler da noch nicht behoben ist?

Vielen Dank!