Comment 8 for bug 806894

Indeed, let's take another look at the query:

select *
from
  CountryLanguage
where (Language, Country) IN (SELECT City.Name, Country.Code FROM ...)

Apparently, one will never get matches when they look for City.Name= CountryLanguage.Language.

On the other hand, in the subquery's join

SELECT City.Name, Country.Code FROM City, Country WHERE Country = Code and Code > 'LLL'

either table will have matches. Condition "City.Country=Country.Code" is the join intended by the dataset, each city lies within some existing country, and each country has some cities.