Creating a Date Dimension Table in Power BI
How can we create a date dimension table in Power BI? We need data such as month name, year, financial quarter, etc. Also, how can we access this data directly with DAX?
A date dimension is an integral part of a data warehouse. A date dimension will have a range of dates with attributes such as Month Name, Year, Financial Quarter, Financial Semester and Financial Year.
In this tip, I will detail a method to create a Date Dimension in Power BI.
In this approach, I will make use of a Power BI calculated table to generate date values. Also I will be adding attributes such as Month Name, Financial Year, Financial Semester and Financial Quarter with the help of DAX.
In a calculated table, the table values are generated by Data Analysis Expression (DAX) and the values are stored in the Power BI model.
DAX Calendar Function
The calendar function returns a table with a single column that contains a continuous set of dates. The start and end date range will be supplied as parameters.
The following formula returns a calculated table with dates between January 1st, 2005 and December 31st, 2015.
=CALENDAR (DATE (2005, 1, 1), DATE (2015, 12, 31))
Creating Date Dimension Calculated table
In the Power BI desktop application, let’s create a new table.
Once the table has been created, now let’s add the DAX expression to generate desirable date values. I will be using the Calendar function to generate date values. In this example, I will be creating date values between 1st January 2015 and 31st December 2020.
=CALENDAR (DATE (2015, 1, 1), DATE (2020, 12, 31))
This function accepts start and end dates as parameters. I have provided the start and end date as “01/01/2015” and “31/12/2020”. Once updated, the Power BI will generate the date values in the query.
Adding Attributes to Date Dimension
Let’s add a year attribute to the table and the DAX expression to calculate the year which is “Year([Date])”.
As above, now let’s add more attributes to the calculated table. I have provided the DAX expression for each attribute below.
Year = YEAR([Date]) Day = Format([Date],"DDDD") DayofMonth = DAY([Date]) MonthofYear = MONTH([Date]) Month = FORMAT([Date], "MMM") & " " & [Year] QuarterofYear = ROUNDUP (MONTH([Date])/3,0) Quarter = "Q" & [QuarterofYear] & " " & [Year] OrdinalDate = DATEDIFF([Year]&",1,1",[Date],DAY)+1 DayofWeek = WEEKDAY([Date],2) WeekEnding = [Date] + (7- [DayofWeek])
The fully extended DateDimension table can be found below.
The data in the calculated table is self-contained and source independent. Based on the configuration of start and end date, the date range can be extended easily. Hence this approach is ideal for reporting and analysis purposes.
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