Złożone zapytanie Postgres

Wszystko, co musisz zrobić, to uruchomić zapytanie zbiorcze:

select sum(t.export) as TotalExport,
sum(t.import) as TotalImport
FROM country c inner join Organization o on c.Country_Code = o.Country_Code
inner join Transaction t on o.organization_code = t.organization_code 

Teraz pytasz:gdzie jest kolumna Korytarz? Odpowiedź brzmi:użyj funkcji string_agg:

select string_agg(DISTINCT c.country, '-' ORDER BY c.country) as Corridor,
sum(t.export) as TotalExport,
sum(t.import) as TotalImport
FROM country c inner join Organization o on c.Country_Code = o.Country_Code
inner join Transaction t on o.organization_code = t.organization_code