Your h-index is the highest number n, such that you have at least n questions/answers, all of which have at least n score.
Q&A for scientific skepticism
Select max(score) from posts where owneruserid=88656
with scores (score, count) as
select 0, (select count(*) from posts where owneruserid=88656 and score>=0)
select * from scores
order by score