Once we speak about knowledge evaluation in Energy BI, making a Date desk is inevitable. There are totally different strategies to create a Date desk both in DAX or in Energy Question. In DAX you my use both CALENDAR() perform or CALENDARAUTO() perform to create the Date desk. In Energy Question you could use a mixture of Record.Dates(), #date() and #length() capabilities. Both manner, there may be one level that’s at all times difficult and it’s easy methods to discover out a correct date vary, ranging from a date up to now and ending with a date sooner or later, that covers all related dates throughout the knowledge mannequin. One easy reply is, we are able to ask the enterprise. The SMEs know what the legitimate date vary is..

Whereas it is a right argument it’s not at all times the case. Particularly with the Begin Date which is a date up to now. In lots of instances the enterprise says:

Lets’s take a look on the knowledge to search out out.

That can be an accurate level, we are able to at all times a have a look at the information, discover all columns with both Date or DateTime datatypes then kind the information in ascending or descending order to get the outcomes. However what if there lots of them? Then this course of could be very time consuming.

A lot of you could already thought that we are able to use CALENDARAUTO() in DAX and we’re good to go. Effectively, that’s not fairly proper. In lots of instances there are some Date or DateTime columns that should not be thought-about in our Date dimension. Like Beginning Date or Deceased Date. Extra on this later on this submit.

On this submit I share a bit of code I wrote for myself. I used to be in a scenario to establish the Begin Date and the Finish Date of the date dimension many occasions, so I assumed it would enable you to as effectively.

The Energy Question expressions I share on this submit begins with getting all current queries utilizing:

• #sections intrinsic variable
• Filtering out the present question identify, which is GetMinMaxAllDates in my pattern, to keep away from getting the next error:

Expression.Error: A cyclic reference was encountered throughout analysis.

• Filtering out the queries which are NOT as sort desk
• Including a brand new structured column named TableSchema that features the tables’ construction
• Increasing the TableSchema structured column retaining the Title and Sort columns and renaming the Title column to Column Title and the Sort column to Datatype
• Filter the outcomes to maintain solely the columns with both Date or DateTime datatypes
• Filtering out pointless values from the Column Title like Beginning Date
• Including a brand new column named Min Date that will get the minimal worth of the column that seems within the Column Title column of the desk worth that seems within the Worth column

Hmm! I suppose it’s an excessive amount of mentioning worth, column and desk in several contexts. I hope I’m not making it much more complicated although.

• Including one other new column named Max Date just like how we created the Min Date
• Extracting the minimal worth of the Min Date column
• Extracting the utmost values of the Max Date column
• Exhibiting the latter two as a listing

So in case you are on the lookout for an answer right here is the Energy Question expressions that I exploit:

let
    AllQueries = #sections,
    RecordToTable = Document.ToTable(AllQueries[Section1]),
    FilterOutCurrentQuery = Desk.SelectRows(RecordToTable, every [Name] <> "GetMinMaxAllDates" and Sort.Is(Worth.Sort([Value]), sort desk) = true),
    AddTableSchemaColumn = Desk.AddColumn(FilterOutCurrentQuery, "TableSchema", every attempt Desk.Schema([Value]) in any other case null),
    ExpandTableSchema = Desk.Buffer(Desk.ExpandTableColumn(AddTableSchemaColumn, "TableSchema", {"Title", "Sort"}, {"Column Title", "Datatype"})),
    FilterTypes = Desk.SelectRows(ExpandTableSchema, every ([Datatype] = "datetime" or [Datatype] = "date")),
    AddedMinDateColumn = Desk.AddColumn(FilterTypes, "Min Date", every Date.From(Record.Min(Desk.Column([Value], [Column Name])))),
    AddedMaxDateColumn = Desk.AddColumn(AddedMinDateColumn, "Max Date", every Date.From(Record.Max(Desk.Column([Value], [Column Name])))),
    FilterOutUnnecessaryColumns = Desk.SelectRows(AddedMaxDateColumn, every ([Column Name] <> "BirthDate")),
    MinDate = Record.Min(Record.Mix({FilterOutUnnecessaryColumns[Min Date], FilterOutUnnecessaryColumns[Max Date]})),
    MaxDate = Record.Max(Record.Mix({FilterOutUnnecessaryColumns[Min Date], FilterOutUnnecessaryColumns[Max Date]})),
    MinMaxDates = {"Min Date = " & Textual content.From(MinDate), "Max Date = " & Textual content.From(MaxDate)}
in
        MinMaxDates

You may obtain the above expressions from right here.

The picture beneath illustrates the outcomes of operating the above code in Energy Question Editor having 11 truth tables and 2 dimension tables. These tables have 17 columns with both Date or DateTime datatypes:

Observe: As soon as once more, that you must go the present question identify within the expressions above. In my case the present question identify is GetMinMaxAllDates as proven within the picture beneath:

Earlier on this submit I discussed that in lots of instances we do NOT need all Date or DateTime columns to be coated by the Date desk. A superb instance for it’s Beginning Date and Deceased Date. If we don’t observe that then we are able to create a whole lot of irrelevant dates in our Date desk like what we get because the Min Date within the above picture which is 10/02/1916. As you may within the picture above there’s a FilterOutUnnecessaryColumns step. We click on on that step to filter the pointless values from the Column Title column as proven within the picture beneath:

Click on on the final step which is MinMaxDates to see the brand new values as proven within the picture beneath:

By operating the above question you get the legitimate date vary, so now you can create a Date desk with any technique of alternative, both in Energy Question or DAX utilizing the above date vary. Bear in mind, creating the Date desk is totally separate course of. This question is simply serving to us discovering minimal and most legitimate dates throughout all tables loaded into the Energy Question Editor.

Please observe that this technique is simply to get the min and max legitimate dates throughout all tables. In the event you try and load the outcomes into the information mannequin in Energy BI, the ensuing desk will likely be empty. This behaviour is the results of utilizing #sections or #shared intrinsic variables in Energy Question and their inherent limitations. Whereas #sections is helpful for accessing metadata about all queries, its dynamic nature may cause issues when attempting to load knowledge into the Energy BI mannequin. Subsequently, we’ve got to Disable question load to keep away from getting an empty desk within the knowledge mannequin.

Concerns

• The above tables altogether have 40M rows and the GetMinMaxAllDates question ran in roughly 10 sec on my machine which isn’t dangerous in any respect. Nevertheless, in bigger tables it might take extra to provide the outcomes
• You will need to have some queries already loaded into the Energy BI Editor
• This technique additionally works in Direct Question mode, however you anticipate the question to take extra time to get the outcomes
• The above question retrieves the min date and max date throughout all tables. Once you create a Date desk, remember that the Date column ought to begin from the 1st Jan of the min date going all the way in which as much as the thirty first Dec of the max date
• This technique works in Energy Question Editor inside Energy BI Desktop RS as effectively
• This technique is NOT supported in Energy BI Dataflows

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