I've forgotten how to do this!
I for each task_number I need to populate null values in field 'bugs_tag'
with the value above it (of the largest lower-numbered row number where the value is not null).
I tried a self-join with a.rowno +1 = b.rowno approach,
but that only gives me one add'l value.
I was trying to avoid subqueries but can do if that's expeditious.