Get related records not in a related table

[swcoop]

So this ask might be a bit much or not the right idea of how to go about it, but I have three sets of tables (the third may not be needed) and I'm trying to get table 3 to be a list of missing records from table 1, where they don't exist in table 2 for each of the dates in that table.

Table 1 is the main set of data and is about vehicles:

ID	Reg
1	abc
2	def
3	ghi
4	jkl
5	mno

Table 2 is a point in time of that vehicle being not available, by day (if they're in this table they're not available)

Date	table1 id
16/01/2024	1
16/01/2024	2
16/01/2024	4
17/01/2024	1
17/01/2024	4

Then table 3 I would like to be the inverse of table 2, so for each date I would like to know the vehicles that are available, as an example based on the above:

Date	table1 id
16/01/2024	3
16/01/2024	5
17/01/2024	2
17/01/2024	3
17/01/2024	5

Logically I can visualise it as: for each unique date that's in table 2, return all ids from table 1 that does not exist in table 2 for that date. But I don't know enough about how to create that in Power BI (or even if that's possible). Hopefully, that makes sense.

[v-tangjie-msft · Accepted solution]

Hi @swcoop ,

According to your description, here are my steps you can follow as a solution.

(1) My test data is the same as yours.

(2) We can create a table.

Table3 = 
 var _a= CROSSJOIN(VALUES('Table2'[Date]),VALUES('Table1'[ID]))
 return  EXCEPT(_a,'Table2')

(3) Then the result is as follows.

Best Regards,

Neeko Tang

If this post  helps, then please consider Accept it as the solution  to help the other members find it more quickly. 

[amustafa]

You can create a 'Table3' as following. See sample data and Power BI file in my shared drive link below.

Table3 =

ADDCOLUMNS(

    CROSSJOIN(Calendar, Table1),

    "Available IDs", IF(

        NOT (COUNTROWS(FILTER(Table2, Table2[Date] = Calendar[Date] && Table2[ID] = Table1[ID])) > 0),

        Table1[ID],

        BLANK()

    ),

    "Unavailable IDs", IF(

        COUNTROWS(FILTER(Table2, Table2[Date] = Calendar[Date] && Table2[ID] = Table1[ID])) > 0,

        Table1[ID],

        BLANK()

    )

)

vehicles_availability