transaction_id, role # 1 или 2
transactions
transaction_id, feedbacks # сумма колонки role для этой transaction_id из верхней таблицы
UPDATE `tt_transactions_events` AS t SET feedbacks = ( SELECT s
FROM (
SELECT f.transaction_id, SUM( `role` ) AS s
FROM `tt_feedbacks` AS f
GROUP BY f.transaction_id )
AS sub_query
WHERE sub_query.transaction_id = t.transaction_id
)