select personID, min(seenTime) as seenTime
from personAttendances
group by personID
如果不是这种情况，并且您确实希望SeenedTime与最小的seeedID相对应（假设seenID是唯一的）：
select a.personID, a.seenTime
from personAttendances as a
join (
-- Get the min seenID for each personID
select personID, min(seenID) as seenID
from personAttendances
group by personID
) as b on a.personID = b.personID
where a.seenID = b.seenID
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