Why does paralelperiod generates a WHERE IN for the different dates

[Anonymous]

Good morning!

Hi I was trying to see what SQL queries does my Power BI report generate for the DB, and in my case i was trying a paralelperiod function to see how it is generated in the DB. I´m using a Direct Query connection to my DB in Vertica. This is the example DAX query:

When I evaluate the query in DAX Studio I get that the selection of DATES for the query is done one by one with an IN. The column D_DT is Date Time format and when I see the SQL query in DAX studio the result is this: 

If you look the scrollbar you realize there is a huge amount of Dates written one by one.

So my doubt is , isn´t this very inefficient? Wouldn´t it be better just to use a BETWEEN or any other way more efficient rather than generate all the DATES that is going to use one by one?

Thanks for your time!

[lbendlin]

SQL Server DateTime Best Practices (mssqltips.com)

[Anonymous · Accepted solution]

@Anonymous 

You may use DATESINPERIOD(). 

DATESINPERIOD function (DAX) - DAX | Microsoft Docs

Paul Zheng

[Anonymous]

Thanks, that is what i was looking for!

[Anonymous]

I have just tried it and it works in the same way. I´m not searching for a practical solution though, I´m just trying to know why it works the way it does and not other way that for me would look more efficient. But thank you anyways for the response.

[lbendlin]

I would agree but the developers probably have a good reason for not using BETWEEN.  Do you know what the compatibility level is for BETWEEN ?

[Anonymous]

Not really ,I was just asking myself why this was the way parallelperiod worked existing the other ways. But I also agree with you, the developers may have a reason for it