I was curious to see the question which are closed and were in the HNQ - for which it is enough to check ClosedDate IS NOT NULL: data.stackexchange.com/math/revision/1066719/1318325/…

Then I was curious to see also questions which were closed at some point (but they are not necessarily closed now). For this I used Posts p INNER JOIN PostHistory ph1 ON (p.Id=ph1.PostId and ph1.PostHistoryTypeId=52) INNER JOIN PostHistory ph2 ON (p.Id=ph2.PostId and ph2.PostHistoryTypeId=10). data.stackexchange.com/math/revision/1066724/1318324/…

Is that ok, or is doing it like this for some reason inefficient.