Part 1 – Parent Child Hierarchies and Pseudo GL Accounts
This post is born out of some real life lessons that I learned while putting together a Financial Data Warehouse based on General Ledger (GL) data i.e. all the GL’s in the foundational financial statements from Net Income and Balance Sheet to Statistical GLs and Cash Flow statements.
While there are many great sources for dimensional modeling, Kimball’s book The Data Warehouse Toolkit: The Complete Guide to Dimensional Modeling (Second Edition) is essential, but there are few resources which discuss dimensional modeling for Financial Data. I am going assume that the reader already has a firm knowledge base of Dimensional Modeling. If not then see my recommendations for books that will help form that foundation: The Start of Something Great.
To be frank this could be a book sized topic in and of it’s self, but I am going to try to cover all the basics so that the reader can avoid the major pit falls.
The first step is gain an understanding of the business processes being modeled (GL creation and maintenance, Period End Close-Out etc..) and the associated requirements (financial statements: Net Income, Balance Sheet, Cash Flow etc…). It is absolutely critical to gain a deep understanding the GL analytical attributes e.g. Business Units, Cost Centers, and Sales Channels. Don’t be surprised when you find out that most of the critical GL attributes are not maintained in any source system but in excel spreadsheets!
I am going to dispense with all the gory details that can be encountered in this process and jump right into the nature and structure of Financial Statements, because their structure will have a significant effect on how the data is modeled.
To make thing easier, I am going to use AdventureWorks as a common point of reference. Here is an example Net Income Statement:
Adventure Works Cube -> Financial Reporting -> rows = named set -> Summary P&L, columns = Amount
I have rearranged the rows from the named set Summary P&L by click and dragging them into something that might look like a financial statement.
A typical financial system will generate financial statements like the one shown above through a series of calculations for each line in the financial statement.
Line/row 5 (Net Sales) = line 2 (Gross Sales) – line 3 (Returns and Adjustments) – line 4 (Discounts)
In other words Net Sales is calculated by aggregating its dependents/children (Gross Sales, Returns and Adjustments, and Discount).
Note: I know that Returns and Discounts need to be subtracted instead of added, I will discuss ways of dealing with that later.
In fact if you look at the rest of the P&L you will realize that all of the line items have a parent child relationship to each other with Net Income being the parent of all the other line items. The following image shows exactly what that a Financial GL Parent Child Hierarchy
might look like.
Create another pivot table by using the following:
Adventure Works Cube -> Financial Reporting -> Rows = Accounts, Columns = Amount
This is the full GL Accounts Parent Child Hierarchy and it is incredibly valuable to providing consistent and flexible financial analysis. The user can drill down to any level starting from the top (Net Income) to the bottom (individual GLs) and preform all their analysis at any level of granularity. Add to that the analytical attributes like Business Unit, Sales Channel, and Cost Center and you have an extremely valuable solution capable of analyzing any part of the company horizontally (GL Hierarchy) and vertically (Analytical attributes which can have their own hierarchies) instantly!!
Note: The full GL Hierarchy not only contains Net Income GL but Balance Sheet and Statistical GLs as well. Net Income is a child of the Balance Sheet which typically goes under one the Current Retained Earnings Accounts.
Take a look at the DimAccount table in the AdventureWorksDW database:
Notice how the Parent of Balance Sheet member is null. That is because Balance Sheet the parent of all GL’s it has no parent.
Ok now that we a explored the potential of the GL Parent Child Hierarchy, the down side that most financial source systems don’t have a nice GL Hierarchy pre-built for you. You are going to have to get business consensus on the structure of the hierarchy and build it yourself. and you will also need to way to manage it once it is built. You will also have to create pseudo GL accounts that don’t already exist in the source system. These pseudo GLs will be parent GLs, like a Balance Sheet or Net Income which be required to complete the calculations in the financial statements.
For example what to do when new GLs are created and where to they go in the hierarchy?
Fortunately, there is a solution for that through Master Data Management. Microsoft’s Master Data Management’s solution is called Master Data Services which handles GL Parent Child Hierarchies very nicely.
Building the GL hierarchy is not a trivial task. The one that I built recently was for a larger company had 180,000 plus GLs. All the GLs (members of the GL Account dimension) had put into exactly the correct order for the calculations to be correct.
The next post will discuss the other critical parts of the Financial DW Solution
Things to consider: Parent Child Hierarchies and Cube performance: