कुछ इस तरह:
select * from UserLog l1
where Operation = 'Enter' and
not exists(select * from UserLog l2
where l1.user = l2.user and
l2.Operation = 'Exit' and
l2.Time > l1.Time)
कुछ इस तरह:
select * from UserLog l1
where Operation = 'Enter' and
not exists(select * from UserLog l2
where l1.user = l2.user and
l2.Operation = 'Exit' and
l2.Time > l1.Time)