This is a multi-part blog post about using DateTime columns in PBI.
It is an area that was traditionally not a focus in PBI.
Classic BI is more interested in daily, monthly, quarterly, and yearly summaries and less in Hours, Minutes, and seconds.
Users of Kusto are many times interested in activities over a very short period of time and in high time accuracy.
If you want to investigate a time period that is relative to the current time, you can use the relative time type of slicer on a DateTime column. Note that the option for relative time is offered also for date columns but it will not work.
The selection can be in the last N hours or last N minutes.
Using the table TransformedSysLogs in the help cluster
With .show queries in the help database you can see a query like:
| where ((["SysLogTimestamp"]) <= ((datetime(2022-02-13 12:58:16.0000000)))) and (((["SysLogTimestamp"]) >= ((datetime(2022-02-13 11:58:16.0000000)))))
| summarize ["a0"]=count() by ["name"], ["facility"], ["host"], ["hostname"]
| limit 1000001
This query is extracting exactly the rows that you want in the most efficient way.
What if the time period you want to investigate is not in the last hours or minutes but is a specific time period like Yesterday between 14:45 and 15:00.
No standard slicer in PBI are able to extract this specific period.
Your only option is to use filters which will appear in the filter pane and not on the page itself.
You first drag the DateTime column to the relevant filter location - Visual, this page or all pages.
Basic filtering is the default but it is not usable and also can be very expensive to setup, as it tries to retrieve all values for the DateTime column. This may fail on a large table
Immediately after you drag the column to the filter pane (Don’t wait for the operation to complete), change the type of filter from basic to advanced and enter the starting time and end time
The user of the report can select any time period using this filter.
You can be as accurate as a single minute.
The query to obtain all the values will run to completion the first time and can consume huge resources.
If you want to avoid wasting resources, you can follow these steps:
- Insert a step in the query that will keep the top 100 rows
- Apply the filter in advanced mode
- Edit the query and remove the keep top rows step
Using this method obtaining the "full" list of DateTime values will run on a small number of rows.
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