SSRS set year variables per record - sql

Question

I need help to create a code to have it display years specified.
User defines years to report: Year1 Year2 Year3
ProductID Year1 data
Year2 data
Year3 data
where even if year 2 has no data like below
ProductID Year1 data
Year2
Year3 data
My current code will show all data that fit the criteria, but will not show Year2 due to no data.
My current code is
select
sales.ProductID, Sales.Trans_Year, Sum(salesQTY) as QTY
from
(select ProductID, Year(Trans_dt) as Trans_Year, salesQTY
from salestable) sales
group by
sales.ProductID, Sales.Trans_Year
My code is inefficient but I did the select twice so that it would group the year on transdate, if any new to make it better would much appreciated.
Hoping to get help to have the following result.
ProductID Year1 QTY
ProductID Year2
ProductID Year3 QTY
Thank you

Answer 1

You can select the years from your table and cross join them to the products to get a matrix of all years and products. The CROSS JOIN will make a record for each year for each product - regardless if the product was sold in that year.
Then LEFT JOIN your sales total. Using a LEFT JOIN will allow the year and product ID from the SALES_YEAR and SALES subqueries to show even if there's none of a product sold in that year.
SELECT PRODUCTS.ProductID, YEARS.SALES_YEAR, SALES.TOTAL_SALES
FROM (
SELECT ProductID
FROM salestable
GROUP BY ProductID
) AS PRODUCTS
CROSS JOIN (
SELECT YEAR(Trans_dt) AS SALES_YEAR
FROM salestable
WHERE YEAR(Trans_dt) IN #YEARS
) AS YEARS
LEFT JOIN (
SELECT ProductID, Year(Trans_dt) as Trans_Year, SUM(salesQTY) AS TOTAL_SALES
FROM salestable
GROUP BY Year(Trans_dt)
) SALES ON SALES.Trans_Year = YEARS.SALES_YEAR AND SALES.ProductID = PRODUCTS.ProductID
Note that this assumes that you sold something every year selected. If the user enter 1905 for the year and there's no data for 1905, that year wouldn't appear. That shouldn't really be an issue though.