So my understanding (please correct me if I'm wrong) is that historical stock data cannot be collected via YQL queries, and I have to use some sort of html query string. That's fine, but I have not been able to find any documentation on how to construct these queries (I've seen a few examples online, but without documentation it's somewhat useless).
I'm very grateful for your help in advance! Thanks.
I'm disappointed with Google's decision as well and have been digging around looking for solutions. With specific reference to Yahoo Finance this link has a post which indicates the info you found on the html query string was reverse engineered, not officially supported and, worse, may violate some TOS agreement. Further down in this discussion, though, someone posted a YQL query to pull data on stock quotes which seems to be officially supported.
Link is: http://developer.yahoo.com/forum/General-Discussion-at-YDN/Using-Yahoo-Finance-API-Not-RSS-/1250246255000-0b82f8f0-7f48-3af2-8fe2-e73a138cbfaa