MS SQL - JOIN show months that doesn't have data - sql

Question

I am having a new problem with SQL JOINS.
Here is my scenario.
I have a report, where I need to show sales performance for a specific customer.
The report shows the sales performance per month.
Please look at my result set:
This is the sales report for customer AFP035. As you can see there are months that are not showing. I am required to include those months that doesn't have data(NULL).
Here what I have tried. I created a month table where I maintained the months.
And then I did a LEFT JOIN. Seems strange because it doesn't show the desired result. From what I understand LEFT JOIN should show the NULL values. And I am wrong.
Please see my query:
select CustNm as company,
Cust as customer,
Cust as custCode,
Mon,
case
when Mon = 1 THEN 'January'
when Mon = 2 THEN 'February'
when Mon = 3 THEN 'March'
when Mon = 4 THEN 'April'
when Mon = 5 THEN 'May'
when Mon = 6 THEN 'June'
when Mon = 7 THEN 'July'
when Mon = 8 THEN 'August'
when Mon = 9 THEN 'September'
when Mon = 10 THEN 'October'
when Mon = 11 THEN 'November'
when Mon = 12 THEN 'December'
end as 'month',
Yr as 'year',
Mon as monthCheck,
case
when NetSales IS NULL THEN 0
else NetSales
end as netSales,
case
when PrvYrSales IS NULL THEN 0
else PrvYrSales
end as prevYearSales,
case
when SalesGrwth IS NULL THEN 0
else SalesGrwth * 100
end as salesGrowth,
case
when YrBfrLst IS NULL THEN 0
else YrBfrLst
end as yearBeforeLast,
case
when BfrLstGrwth IS NULL THEN 0
else BfrLstGrwth * 100
end as yearBeforeLastGrowth
from BigEMasterData.dbo.monthtmp as a
left outer join BigESales.dbo.tbl_ReportCOMPANYperCust as b
on b.Mon = a.monthNo
or b.Mon is null
The result is the screenshot above.
Would you help me with this or at least enlighten me why I am not getting the desired result?
Thank you so much. Any suggestion would be highly appreciated.
EDIT: SOLVED: with Yogesh's help Thankyou.
;WITH CTE AS (
SELECT * FROM tbl_ReportCOMPANYperCust r
WHERE Cust = 'AFP035'
and Yr = 2016
)
SELECT
r.CustNm as company, r.Cust as customer, r.Cust as custCode,
a.monthNo, a.monthName, r.Yr as Year,
COALESCE(NetSales, 0) as netSales,
COALESCE(PrvYrSales, 0) as prevYearSales,
COALESCE(SalesGrwth*100, 0) as salesGrowth,
COALESCE(YrBfrLst, 0) as yearBeforeLast,
COALESCE(BfrLstGrwth*100, 0) as yearBeforeLastGrowth
FROM BigEMasterData.dbo.monthtmp a
LEFT OUTER JOIN CTE r on r.Mon = a.monthNo
Here is the result. :

Answer 1

Let me correct your query, in order to get the all months then your calendar table should first table
SELECT
r.CustNm as company, r.Cust as customer, r.Cust as custCode,
a.monthNo, a.MontName, r.Yr as Year,
COALESCE(NetSales, 0) as netSales,
COALESCE(PrvYrSales, 0) as prevYearSales,
COALESCE(SalesGrwth*100, 0) as salesGrowth,
COALESCE(YrBfrLst, 0) as yearBeforeLast,
COALESCE(BfrLstGrwth*100, 0) as yearBeforeLastGrowth
FROM monthtmp a
LEFT OUTER JOIN tbl_ReportCOMPANYperCust r on r.Mon = a.monthNo
Use ANSI SQL Standard COALESCE() function to check NULL values
In order to get all months name use CTE or Subquery which could hold the filtered records
;WITH CTE AS (
SELECT * FROM tbl_ReportCOMPANYperCust r
WHERE Cust = 'AFP035'
and Yr = 2016
)
SELECT
COLAESCE(r.CustNm, LAG(r.CustNm) OVER (ORDER BY a.monthNo)) as company,
COLAESCE(r.Cust, LAG(r.Cust) OVER (ORDER BY a.monthNo)) as customer,
COLAESCE(r.Cust, LAG(r.Cust) OVER (ORDER BY a.monthNo)) as custCode,
a.monthNo, a.monthName, r.Yr as Year,
COALESCE(NetSales, 0) as netSales,
COALESCE(PrvYrSales, 0) as prevYearSales,
COALESCE(SalesGrwth*100, 0) as salesGrowth,
COALESCE(YrBfrLst, 0) as yearBeforeLast,
COALESCE(BfrLstGrwth*100, 0) as yearBeforeLastGrowth
FROM BigEMasterData.dbo.monthtmp a
LEFT OUTER JOIN CTE r on r.Mon = a.monthNo

Answer 2

You would appear to want:
SELECT c.company, c.customer, c.custCode,
m.monthNo, m.monthName, c.Year,
COALESCE(r.NetSales, 0) as netSales,
COALESCE(r.PrvYrSales, 0) as prevYearSales,
COALESCE(r.SalesGrwth*100, 0) as salesGrowth,
COALESCE(r.YrBfrLst, 0) as yearBeforeLast,
COALESCE(r.BfrLstGrwth*100, 0) as yearBeforeLastGrowth
FROM (SELECT DISTINCT r.CustNm as company, r.Cust as customer, r.Cust as custCode, r.Yr as Year
FROM tbl_ReportCOMPANYperCust
WHERE c.Cust = 'AFP035'
) c CROSS JOIN
BigEMasterData.dbo.monthtmp m LEFT OUTER JOIN
tbl_ReportCOMPANYperCust r
ON r.Mon = m.monthNo AND r.Cust = c.customer
ORDER BY m.monthNo;
Notice the CROSS JOIN. This brings in the initial columns, so you have them even for months that do not match the data.