Complex Postgres query

Question

I have a db schema like following -

(Country table)
| Country | Country Code| 
-------------------------
    ABC         A 
    BCD         B

Answer 1

All you need to do is to run an aggregate query:

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 

Now, you ask: where is the Corridor column? The answer is: use the string_agg function:

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