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select 'User 1' sendingUser, 'User 2' ReceivingUser, Cast('08/01/2021' as date) [timestamp] into t union all
select 'User 3', 'User 4', '08/01/2021' union all
select 'User 2', 'User 1', '08/01/2021' union all
select 'User 1', 'User 2', '08/02/2021' union all
select 'User 3', 'User 4', '08/02/2021' union all
select 'User 1', 'User 2', '08/03/2021'
6 rows affected
hidden batch(es)
select sendinguser, ReceivingUser, Count(*) MessageCount
from t
where timestamp between '20210801' and '20210831'
group by sendinguser,ReceivingUser
order by sendinguser
