# MDX Utility Belt of Calculations Part 1

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Developing MDX calculations is one of the most confusing and time consuming pieces of building an Analysis Services cube.  That is why I have accumulated what I like to call a Utility Belt of calculation that I can pull out at any moment to solve a problem.  I consider this a Utility Belt because on just about every Analysis Services project that I have worked on these calculations have come in handy and I hope they will be helpful for you.

When building calculations you may find the templates that are available in Business Intelligence Development Studio (BIDS) as a helpful starting point.  Unfortunately, I have found even using these templates can make calculations more confusing than they really need to be.

In this blog series I will give you the business problem, solution, and then calculation that satisfies the business problem.

Problem

You need to return sales for one year prior (Ex. one year ago, four quarters ago, twelve months ago).

Solution

Use the ParrallelPeriod time series function to look back a set number of values back in a date hierarchy and return the sales at that point.

Calculations

Looking back one year at the Year level

(ParallelPeriod([Date].[Date Hierarchy].[Year],
1,
[Date].[Date Hierarchy].CurrentMember),
[Measures].[Sales Amount])

---------------------------------------------------------------

Looking back four quarters at the Quarter level

(ParallelPeriod([Invoice Date].[Date Hierarchy].[Quarter],
4,
[Invoice Date].[Date Hierarchy].CurrentMember),
[Measures].[Sales Amount])

---------------------------------------------------------------

Looking back twelve months at the Month level

(ParallelPeriod([Invoice Date].[Date Hierarchy].[Month],
12,
[Invoice Date].[Date Hierarchy].CurrentMember),
[Measures].[Sales Amount])

You can find me regularly blogging at http://www.bidn.com/blogs/DevinKnight

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