SUM with left outer join gets inflated result - sql

Question

The following query gives me the MRR (monthly recurring revenue) for my customer:
with dims as (
select distinct subscription_id, country_name, product_name from revenue
where site_id = '18XLsHIVSJg' and subscription_id is not null
)
select to_date('2022-07-01') as occurred_date,
count(distinct srm.subscription_id) as subscriptions,
count(distinct srm.receiver_contact) as subscribers,
sum(srm.baseline_mrr) as mrr_srm
from subscription_revenue_mart srm
join dims d on d.subscription_id = srm.subscription_id
where srm.site_id = '18XLsHIVSJg'
-- MRR as of the day before ie June 30th
and to_date(srm.creation_date) < '2022-07-01'
-- Counting the subscriptions active after July 1st
and ((srm.subscription_status = 'SUBL.A') or
-- Counting the subscriptions canceled/deactivated after July 1st
(srm.subscription_status = 'SUBL.C' and (srm.deactivation_date >= '2022-07-01') or (srm.canceled_date >= '2022-07-01')) ) group by 1;
I get a total of $5922.15 but I need to add data from another table to capture upgrades/downgrades a customer makes on a product subscription. Using the same approach as above, I can query my "change" table thusly:
select subscription_id, sum(mrr_change_amount) mrr_change_amount,max(subscription_event_date) subscription_event_date from subscription_revenue_mart_change srmc
where site_id = '18XLsHIVSJg'
and to_date(srmc.creation_date) < '2022-07-01'
and ((srmc.subscription_status = 'SUBL.A')
or (srmc.subscription_status = 'SUBL.C' and (srmc.deactivation_date >= '2022-07-01') or (srmc.canceled_date >= '2022-07-01')))
group by 1;
I get a total of $3635.47
When I combine both queries into one, I get an inflated result:
with dims as (
select distinct subscription_id, country_name, product_name from revenue
where site_id = '18XLsHIVSJg' and subscription_id is not null
),
change as (
select subscription_id, sum(mrr_change_amount) mrr_change_amount,
-- there can be multiple changes per subscription
max(subscription_event_date) subscription_event_date from subscription_revenue_mart_change srmc
where site_id = '18XLsHIVSJg'
and to_date(srmc.creation_date) < '2022-07-01'
and ((srmc.subscription_status = 'SUBL.A')
or (srmc.subscription_status = 'SUBL.C' and (srmc.deactivation_date >= '2022-07-01') or (srmc.canceled_date >= '2022-07-01')))
group by 1
)
select to_date('2022-07-01') as occurred_date,
count(distinct srm.subscription_id) as subscriptions,
count(distinct srm.receiver_contact) as subscribers,
-- See comment RE: LEFT OUTER join
sum(coalesce(c.mrr_change_amount,srm.baseline_mrr)) as mrr
from subscription_revenue_mart srm
join dims d
on d.subscription_id = srm.subscription_id
-- LEFT OUTER join required for customers that never made a change
left outer join change c
on srm.subscription_id = c.subscription_id
where srm.site_id = '18XLsHIVSJg'
and to_date(srm.creation_date) < '2022-07-01'
and ((srm.subscription_status = 'SUBL.A')
or (srm.subscription_status = 'SUBL.C' and (srm.deactivation_date >= '2022-07-01') or (srm.canceled_date >= '2022-07-01'))) group by 1;
It should be $9557.62 ie (5922.15 + $3635.47) but the query outputs $16116.91, which is wrong.
I think the explode-implode syndrome may cause this.
I had designed my "change" CTE to prevent this by aggregating all the relevant fields but it's not working.
Can someone provide pointers on the best way to work around this issue?

Answer 1

It would help if you gave us sample data too, but I see a problem here:
sum(coalesce(c.mrr_change_amount,srm.baseline_mrr)) as mrr
Why COALESCE? That will give you one of the 2 numbers, but I guess what you want is:
sum(ifnull(c.mrr_change_amount, 0) + srm.baseline_mrr) as mrr
That's the best I can offer with what you've given us.