Slowly Changing Dimension (SCD) in Power BI, Part 1, Introduction to SCD

Slowly changing dimension (SCD) is a data warehousing concept coined by the amazing Ralph Kimball. The SCD concept deals with moving a specific set of data from one state to another. Imagine we have a human resources (HR) system; Stephen Jiang is a Sales Manager, managing 10 sales representatives in his team. The following screenshot shows the sample data:

SCD in Power BI, Stephen Jiang is the sales manager of a team of 10 sales representatives
Image 1: Stephen Jiang is the sales manager of a team of 10 sales representatives

Today, Stephen Jiang got his promotion to the Vice President of Sales role, so his team has grown in size from 10 to 17. Stephen is the same person, but his role is now changed, as shown in the following image:

SCD in Power BI, Stephen's team after he was promoted to Vice President of Sales
Image 2: Stephen’s team after he was promoted to Vice President of Sales

Another example is when a customer’s address changes in a sales system. Again, the customer is the same, but their address is now different. From a data warehousing standpoint, we have different options to deal with the data depending on the business requirements, leading us to different types of SDCs. It is crucial to note that the data changes in the transactional source systems (in our examples, the HR system or a sales system). We move and transform the data from the transactional systems via extract, transform, and load (ETL) processes and land it in a data warehouse, where the SCD concept kicks in. SCD is about how changes in the source systems reflect the data in the data warehouse. These kinds of changes in the source system do not happen very often hence the term slowly changing. Many SCD types have been developed over the years, which is out of the scope of this post, but for your reference, we cover the first three types as follows.

SCD type zero (SCD 0)

With this type of SCD, we ignore all changes in a dimension. So, when a person’s residential address changes in the source system (an HR system, in our example), we do not change the landing dimension in our data warehouse. In other words, we ignore the changes within the data source. SCD 0 is also referred to as fixed dimensions.

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Quick Tips: Time Dimension with Time Bands at Seconds Granularity in Power BI and SSAS Tabular

Time Dimension with Time Bands at Seconds Granularity in Power BI and SSAS Tabular

I wrote some other posts on this topic in the past, you can find them here and here. In the first post I explain how to create “Time” dimension with time bands at minutes granularity. Then one of my customers required the “Time” dimension at seconds granularity which encouraged me to write the second blogpost. In the second blogpost though I didn’t do time bands, so here I am, writing the third post which is a variation of the second post supporting time bands of 5 min, 15 min, 30 min, 45 min and 60 min while the grain of the “Time” dimension is down to second. in this quick post I jump directly to the point and show you how to generate the “Time” dimension in three different ways, using T-SQL in SQL Server, using Power Query (M) and DAX. Here it is then:

Time Dimension at Second Grain with Power Query (M) Supporting Time Bands:

Copy/paste the code below in Query Editor’s Advanced Editor to generate Time dimension in Power Query:

let
Source = Table.FromList({1..86400}, Splitter.SplitByNothing()),
#"Renamed Columns" = Table.RenameColumns(Source,{{"Column1", "ID"}}),
#"Time Column Added" = Table.AddColumn(#"Renamed Columns", "Time", each Time.From(#datetime(1970,1,1,0,0,0) + #duration(0,0,0,[ID])), Time.Type),
    #"Hour Added" = Table.AddColumn(#"Time Column Added", "Hour", each Time.Hour([Time]), Int64.Type),
    #"Minute Added" = Table.AddColumn(#"Hour Added", "Minute", each Time.Minute([Time]), Int64.Type),
    #"5 Min Band Added" = Table.AddColumn(#"Minute Added", "5 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/5) * 5) + 5, 0)), Time.Type),
    #"15 Min Band Added" = Table.AddColumn(#"5 Min Band Added", "15 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/15) * 15) + 15, 0)), Time.Type),
#"30 Min Band Added" = Table.AddColumn(#"15 Min Band Added", "30 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/30) * 30) + 30, 0)), Time.Type),
#"45 Min Band Added" = Table.AddColumn(#"30 Min Band Added", "45 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/45) * 45) + 45, 0)), Time.Type),
#"60 Min Band Added" = Table.AddColumn(#"45 Min Band Added", "60 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/60) * 60) + 60, 0)), Time.Type),
    #"Removed Other Columns" = Table.SelectColumns(#"60 Min Band Added",{"Time", "Hour", "Minute", "5 Min Band", "15 Min Band", "30 Min Band", "45 Min Band", "60 Min Band"})
in
    #"Removed Other Columns"
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Power BI Governance, Good Practices, Part 1: Multiple Environments, Data Source Certification and Documentation

Power BI Governance, Good Practices, Part 1: Multiple Environments, Data Source Certification and Documentation

Power BI is taking off, and it’s fast becoming the most popular business intelligence platform on the market. It’s easy to engage with and get professional results quickly, making it the perfect tool for organisations looking to beef up their BI prowess and make data driven decisions through-out the organisation.

Gartner 2020 Magic Quadrant for Analytics and Business Intelligence Platforms
Did you know that Gartner named Microsoft as the 2020 leader in their Magic Quadrant for Analytics and Business Intelligence Platforms?

In this post we’re going to look at three good practices for implementation and give you the tips you need to make sure you avoid common pitfalls so you are on the fast track to success with Power BI on your organisation.

1. Setup multiple environments

When working on a Power BI implementation project, it’s wise to have multiple environments to manage the lifecycle of your BI assets. Below we’ve listed several environments that should be considered depending on the complexity of the project and your organisation’s needs.

Development (aka Dev)

Being able to keep on top of the many reports you’re testing, and having the ability to track changes that occur, is essential as you get setup. Without a specific Dev environment, your production environment will quickly become overwhelmed with assets, making it hard to maintain and manage.  

When working in the dev environment, make sure that you have data sources specifically for development. We’ve seen production data used in dev on many occasions which can lead to serious privacy and data sovereignty issues. Your dev data sources shouldn’t contain sensitive data. 

These development environments can be on your local network or in cloud storage (like OneDrive for Business or GitHub). It is recommended to have separate Workspaces in Power BI Service for each environment.

Tip: The data sources of all published reports to Power BI Service must be sufficient for development use only and should avoid including confidential data.

User Acceptance Testing (aka UAT) 

The people who will be using the reports daily are the ones who should be testing them – they know the business best, and will be able to identify opportunities and gaps that the development team may not be able to identify themselves. By making sure the user is brought into the process early on, it maximises the value added to the business.

User acceptance testing is the last phase of testing. The UAT environment should only be created once the solution has been fully tested in Dev and approved by senior Power BI developers.

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