prova detta:
WITH Credits_added AS (
SELECT CreditLogId, OccurredOn, credits
, SUM(credits) OVER (ORDER BY CreditLogId) - credits AS b --before
, SUM(credits) OVER (ORDER BY CreditLogId) AS a --after
, GivenByUserCode
FROM @CreditLogs
WHERE Credits > 0)
, Credits_spent AS (
SELECT CreditLogId, OccurredOn, credits
, SUM(credits) OVER (ORDER BY CreditLogId) * -1 + credits AS b
, SUM(credits) OVER (ORDER BY CreditLogId) * -1 AS a
FROM @CreditLogs
WHERE Credits < 0)
SELECT s.CreditLogId, s.OccurredOn
, CASE WHEN a.a > s.a THEN s.a ELSE a.a END - CASE WHEN a.b > s.b THEN a.b ELSE s.b END AS Credits
, a.GivenByUserCode
FROM Credits_added AS a
INNER JOIN Credits_spent AS s ON a.a > s.b AND s.a > a.b