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Helper II

Find entry whose date time is less than but closest to fact table

I am looking for logic to determine how to pull the following data

I have a fact table that has transaction date and time and computer per transaction the second table is the device table showing who was logged into the device (there is no log out). My intended logic will be to link date, and device ID and then find the time that is the first time found less the log in time from the fact table . So the first entry I want to determine BOB was logged and second ROB

Date      Time        Device

Example :      1/1/17   08:10:53   RFGN3550

1/1/17   10:13:40   RFGN3560

I have a device Log table that says who was logged into that device

Example:           1/1/17   08:00:00   RFGN3550     BOB

1/1/17  09:00:00    RFGN3550     MARY

1/1/17  09:00:00    RFGN3560     SAM

1/1/17  10:00:00    RFGN3550    ROB

2 ACCEPTED SOLUTIONS
Super User

This seems to have been deemed an M question, but here is one of those "dime a dozen" DAX solutions:

PBIX sample

Calculated column in Transactions:

```Person =
VAR TransactionDateTime = Transactions[DateTime]
RETURN
CALCULATE (
//Arbitrary tie-breaker
CALCULATETABLE (
)
)```

Owen 🙂

Owen Auger

My Blog
Community Champion

@brett_walton

I suspect you've modified @OwenAuger's formula to only look at your Time columns!

Note that he checks a Date/Time column.

So to address this create a Date-Time Column in both tables like this

`Date-Time = [Date]&" "&[Time]`

Both of these columns will default to Text - so you need to convert them to Data Type - Date/Time - again in both tables.

This should resolve it!

Good Luck!

15 REPLIES 15
Community Champion

@brett_walton wrote:

Date      Time        Device

Example :      1/1/17   08:10:53   RFGN3550

1/1/17   10:13:40   RFGN3560

I have a device Log table that says who was logged into that device

Example:           1/1/17   08:00:00   RFGN3550     BOB

1/1/17  09:00:00    RFGN3550     MARY

1/1/17  09:00:00    RFGN3560     SAM

1/1/17  10:00:00    RFGN3550    ROB

Sam is the only one logged in device 3560!

Maybe you meant to have Rob log in device 3560 - but as you've written it the second should be Sam

Super User

This seems to have been deemed an M question, but here is one of those "dime a dozen" DAX solutions:

PBIX sample

Calculated column in Transactions:

```Person =
VAR TransactionDateTime = Transactions[DateTime]
RETURN
CALCULATE (
//Arbitrary tie-breaker
CALCULATETABLE (
)
)```

Owen 🙂

Owen Auger

My Blog
Helper II

Thank you Owen, that worked well.  I perferred the DAX solution over M as I actaully understand what you did.   (work for a smaller company so I am not a full time data person) .

One other huddle I need to cross

If I have a transaction at 1/27/17 @ 00:10:00 AM AND the log in record am looking for is 1/26/17  22:40:00 (so they logged in the previous day) - is there another condition I can add to this to account for that ?

Thank You Again

Brett

Community Champion

@brett_walton

I suspect you've modified @OwenAuger's formula to only look at your Time columns!

Note that he checks a Date/Time column.

So to address this create a Date-Time Column in both tables like this

`Date-Time = [Date]&" "&[Time]`

Both of these columns will default to Text - so you need to convert them to Data Type - Date/Time - again in both tables.

This should resolve it!

Good Luck!

Helper II

Thank you , I noticed the merge I just didnt do 2 things 1) change my data type 2) open my device log fact tbale for mutiple days

Community Champion

The other thing this community will agree on @OwenAuger's solutions definitely do not fall in the "dime a dozen" category!

BTW Owen's sample file above includes Marcel's solution as well @MarcelBeug

@brett_waltonyou can create the Device table in Owen's solution in the Query Editor

Duplicate the table that has ALL Devices (right-click the table)

Rename It

Remove All Other Columns

Remove Duplicates (right-click the column)

Close and Apply

Good Luck!

Community Champion

Maybe DAX would be more appropriate, but in M (Edit Queries) it can be done with the following code.

I combined dates and times in each table to the field "DateTime".

Steps:

• Merge table Logins with Transactions (Logins are nested tables in Transctions table)
• Expand the nested table, returning only the name
• Apply type text to the Name

```let
LatestLogin = Table.TransformColumns(RemovedLogins, {{"Logins before Transaction", each Table.SelectRows(_, let latest = List.Max(_[DateTime]) in each _[DateTime] = latest)}}),
in
Typed```

By the way, the second is SAM, not ROB.

Specializing in Power Query Formula Language (M)
Helper II

Thank you .. Will give it a try but for point of clarity of what I am looking for the second one is Rob . The transaction was at 10:13 and he logged into the device at 10:00 so it was he who posted it not SAM .

Community Champion

Folks it seems @MarcelBeug maybe giving our undisputed M expert @ImkeF a run for her money!

Community Champion

Thanks @Sean, @ImkeF is aware.

Specializing in Power Query Formula Language (M)
Super User

Happy to hand-over 🙂

Imke Feldmann (The BIccountant)

If you liked my solution, please give it a thumbs up. And if I did answer your question, please mark this post as a solution. Thanks!

Community Champion

@ImkeFif we can poll this community one thing will be certain!

When it comes to DAX there are many so called "experts"

But when it comes to M everyone will vote for you!

So don't hand over anything yet!

Community Champion

When it comes to theoretical M knowledge, I think @ImkeF can more or less compete by now.

With regard to practical experience I'm definitely lagging behind.

But I have that screencasting software as a card in my sleeve.

And my userid is with a capital M...

Specializing in Power Query Formula Language (M)
Community Champion
Community Champion

@Sean Especially with Power Query I think that videos have enormous added value, as code is typically generated by clicking the right buttons on the menus.

A good example in https://community.powerbi.com/t5/Desktop/Parsing-Embedded-JSON/m-p/118765#M50133 in which the solution is basically simple and straightforward, but it requires a lot of clicks.

Even with a video it takes 3 minutes to explain.

Specializing in Power Query Formula Language (M)

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