Add variance in the rows of table - reporting-services

Question

I've a SSRS report which should look like below,
--------------------------------
Year Product Total customers
--------------------------------
2015 prd1 100
prd2 50
prd3 60
2014 prd1 80
prd2 60
prd3 60
Varience
Prd1 20
Prd2 -10
Prd3 0
I've done the year wise grouping and the data mapping. But I'm not sure how to add variance(between 2015-2014) in each row based on the each product of the year
Update:
My dataset looks like this
Year CategoryId CategoryDesc TotalCustomerCount
2013 Prd1 Testproduct 100
2013 Prd2 Testprod2 50
2013 Prd3 Tesrprod3 45
2014 Prd1 Testproduct 80
2014 Prd2 Testprod2 60
You can see that some products may miss out in a year.
Note: The dataset is created from a Dimesional cube and not from SQL queries.

Answer 1

It is kind of hard to tell exactly without knowing what your current dataset looks like.
But I believe that Stanislovas' example will be of little use to you because his example only works if your dataset has a single row for each product, with columns with the total for each year. Which I'm guessing you do not have because you used row grouping to get the above result. If you did, you could've used column-grouping instead of row-grouping to get a better overview.
You have two possibilities:
Replace your current dataset completely with a dataset that has columns for each year value (like in Stanislovas' example). To achieve this kind of dataset you need your query to look like this for example:
SELECT DISTINCT(myTable.Product), t1.Total AS 'Total2014', t2.Total AS 'Total2015'
FROM myTable
JOIN (SELECT Product, SUM(Total) AS Total
FROM myTable
WHERE Year = 2014
GROUP BY Product) as t1 ON t1.Product = myTable.Product
JOIN (SELECT Product, SUM(Total) AS Total
FROM myTable
WHERE Year = 2015
GROUP BY Product) as t2 ON t2.Product = myTabel.Product
This can then be used to make a table that looks like this:
---------------------------------------
| Product | 2014 | 2015 | Variance |
---------------------------------------
| prd1 | 100 | 80 | 20 |
| prd2 | 50 | 60 | -10 |
| prd3 | 60 | 60 | 0 |
...
Or you can add a second datasource that has calculated these differences before sending it to the reporter. Here is an example to help you with your query: https://stackoverflow.com/a/15002915/4579864
If you need any more help, just leave a comment and I'll try and explain furthur. This should at least get you started.

Answer 2

I think the easiest way to handle this requeriment is generating the data from the query using T-SQL. However the output you require can be produced from SSRS using a dataset with the same structure as the dataset you provided in the update.
In order to recreate your scenario I used this dataset.
Year Product CategoryDesc TotalCustomerCount
2013 Prd1 Testproduct 100
2013 Prd2 Testprod2 50
2013 Prd3 Tesrprod3 45
2014 Prd1 Testproduct 80
2014 Prd2 Testprod2 60
My approach is take the minimum and maximum year values (2013 and 2014) and the product in every row and look up the TotalCustomerCount to substract it. This is a step by step guide.
First, create a calculated field in your dataset. Right click the dataset in Report Data pane, call it Year_Product and set this expression in the field source textbox.
=Fields!Year.Value & "-" & Fields!Product.Value
This will produce an additional field called Year_Product which has Year and Product fields concatenated with the - character in middle. In example: 2013-Prd1, 2014-Prd1, 2013-Prd3 etc.
Now create a tablix with this data arrangement:
In the cell highlighted in red use this expression:
=Lookup(Max(Fields!Year.Value,"DataSet13") & "-" &
Fields!Product.Value,Fields!Year_Product.Value,Fields!TotalCustomerCount.Value,"DataSet13")
-
Lookup(Min(Fields!Year.Value,"DataSet13") & "-" &
Fields!Product.Value,Fields!Year_Product.Value,Fields!TotalCustomerCount.Value,"DataSet13")
This will look up the max year and product of the row in the Year_Product field and get the TotalCustomerCount.
Year_Product: 2014-Prd1 and TotalCustomerCount: 80
Year_Product: 2013-Prd1 and TotalCustomerCount 100
The above example produces -20 since 80 - 100 = -20
It will show us repeated products because every product may be present two times. To avoid this it is necessary to sort the tablix by Product, go to tablix properties and set the below sorting option.
Now hide duplicated rows. Go to tablix properties / Row visibility and select Show or hide based on an expression.
Use this expression ton conditionally hide the duplicated products:
=IIF(
Fields!Product.Value=PREVIOUS(Fields!Product.Value),
true,
false
)
Finally if you preview the report you will see something like this (I recreated your both tables.)
Note I am using only one dataset, the same that you provide in your
question.
Hopefully this what you are looking for let me know if you need further help.