I have a very simple query
SELECT o.*,sl.Market,sl.Category FROM _Open o WITH (NOLOCK) INNER JOIN SendLog sl WITH (NOLOCK) ON o.JobID = sl.JobID WHERE o.JobID IN (3103648)
Which is trying to get records from the _Open table and join them with the SendLog table to get Market and Category.
My Data Extension has 3 columns JobID, Market and Category.
The query above was more complex, but I stripped it down to the fundamentals, bare bones.
Yet that query is giving me 29+ million rows on a send that was only about 7k. I even filtered off of the SendLog for the Category column for the value from last night's send, and that yielded 29 million rows. So something is off. It seems like it's duplicating rows or something. My query seems correct, so I'm not sure what the deal is. For the record, I have NEVER had success querying the SendLog, I always have issues.