How to combine horizontally the results of two queries?

Question

SQL

A meaningless, but simple pseudo-language example
SELECT contract AS ct, contractDate, subscriber, (SELECT cost FROM upload WHERE contract = ct)
FROM upload
That is, I want to somehow pass the value of the contract inside to use it in the condition there. Is it possible to do this?
PS The client can have international and long-distance calls, it is necessary that the request displays the cost of both in one line. If you use normal grouping, the output will be two lines. And my question assumes something like UNION, but only horizontally.

Answer 1

LEFT JOIN - to include fields from other tables
GROUP BY to join rows on selected fields

SELECT contract , contractDate, subscriber, SUM( cost ) AS 'cost'
FROM upload
GROUP BY contract , contractDate, subscriber

Adds cost for identical contract , contractDate, subscriber fields

Answer 2

Select ct,
  contractDate,
        subscriber,
  'Междугордние',
  [Междугордние],
  'Международные',
  [Международные]
from (SELECT [contract] AS ct, contractDate, subscriber,[тип_звонка],cost  from upload ) t
  pivot (sum([cost]) for [тип_звонка] in ([Междугордние],[Международные])) pvt