In this blog post we’ll take a quick look at using ConcatenateX function to view a concatenated string of dates where the max daily sales occurred for a given month.

I came across this function whilst going through the excellent “Mastering DAX 2nd Edition Video Course” by the guys from SQLBI.com. So credit to Marco and Alberto for sharing this.

So how does it work? If we had a list of dates ranging from 01/01/2020 to 31/12/2020 and we wanted to see which days we achieved maximum sales for each given month in a year we could use the ConcatenateX function to return these dates in a single row per month.

As we can see in the screenshot below, the left hand table shows the month of June where we achieved maximum sales for in June on both 18/06/2020 and 25/06/2020 of 99. In the table to the right we can see those two dates presented on a single row for the month of June in the column “What were the max days?”. This was column was created using the ConcatenateX function!

So let us first look at what the maximum daily sales were per month. To do this we’ll use the MAXX function to create “Max Daily Sales”. This returns the maximum daily sales rate achieved for each given month as a single value. So for the month of June this would be 99. The problem with this is we are not sure which days these max sales were achieved on without drilling down into the data.  Was this just one day or was it multiple days? All we can see is a figure of 99.

So let us create a new measure to work out on which days this figure of 99 occurred on.

The variable at point (a) returns a table with a single column which lists all of the unique dates in our Sales_2020 table.

The variable at point (b) returns the max sales for the given filter context in this case month.

The variable at point (c) uses the filter function to filter out only the days where the max sales were achieved by setting the total quantity sold measure to the max daily sales variable. For example in June we achieved max daily sales of 99 on 18/06/2020 and 25/06/2020. Therefore the variable at point (c) would filter out the ListOfDays table variable to just 18/06/2020 and 25/06/2020 only.

If we just had one max sales day per month we could simply return MaxDaysOnly. However we may have multiple days per month where max sales were achieved. Hence we use the ConcatenateX function to create a string of dates.

The variable at point (d) creates a string of concatenated dates separated by the delimiter “,” which can be used against a single row in a table.

Wrapping it all up returns us this table below, which shows us which days max sales were achieved per given month! Pretty cool eh?