How to merge dates between 2 locations using SQL? - sql

Question

TIA for any assistance towards this problem, I am rather new to SQL/SSMS.
I would like to understand how I can create date rows for 1 location based on another. For example, I have the following table:
ClientFK | LocationFK | Month | Sales
---------|------------|-----------|-------
15 |1 |2019-04-01 | $100
15 |2 |2019-04-01 | $50
15 |2 |2019-03-01 | $30
15 |2 |2019-02-01 | $20
How can I create rows in location 1 in which location 2 had sales? The output would look like this:
ClientFK | LocationFK | Month | Sales
---------|------------|-----------|-------
15 |1 |2019-04-01 | $100
15 |1 |2019-03-01 | $0
15 |1 |2019-02-01 | $0
15 |2 |2019-04-01 | $50
15 |2 |2019-03-01 | $30
15 |2 |2019-02-01 | $20
My goal is to make this dynamic, so I'm not trying to work with this specific client/location, it is just an example. Ideally this should work for any client/location combo.
Again, I'm rather new to this, and wasn't sure how to best ask this question. Any advice on how to clarify what I'm asking would be much appreciated as well. Thanks!

Answer 1

This will give you all months for all locations and all clients.
with AvailableDates as(
select distinct [Month] from MonthlySales
),
Locations as(
select distinct LocationFk from MonthlySales
),
Clients as(
select distinct ClientFk from MonthlySales
)
select c.ClientFk, l.LocationFk, ad.Month, IsNull(ms.Sales,0) as Sales
from Locations l
left join AvailableDates ad on 1=1
left join clients c on 1=1
left join MonthlySales ms on
l.LocationFk=ms.LocationFk
and c.ClientFk = ms.ClientFk
and ad.Month = ms.Month
order by locationFK, Month desc

Answer 2

Here is a way to go about with this. First find out all of the unique months for Location2.
Then carterisan prod with the Client1 data.
After that you have all of the records for Client1 and Client2 in the carteisan prod block, which would left join with the data and set up the sales=0 for those missing months data.
with loc2_data
as (select distinct month
from tbl
where locationfk=2
and ClientFK=15
)
,cartesian_prod
(
select a.ClientFK,a.LocationFK,b.Month
from tbl a
join loc2_data b
on 1=1
where a.locationfk=1
and a.ClientFK=15
)
select a.ClientFK,a.LocationFK,a.Month,isnull(v.Sales,0) as sales
from cartesian_prod a
left join tbl v
on a.ClientFK=v.ClientFK
and a.LocationFK=v.LocationFK
and a.Month=v.Month