[SQL] Join two SQL queries to return one response and join same rows

I received an answer like the image below (A) using the following query. How should I change the query to get a response like image B? so that each username has one line.

SELECT userName,userId, SUM(amount) AS debit, 0 as credit
FROM debts
where buyerId != userId
GROUP BY userName,userId

UNION ALL

SELECT buyer,buyerId, 0 as total_debit, SUM(amount) AS credit
FROM debts
where buyerId != userId
GROUP BY buyer,buyerId

ORDER BY buyerId




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