Not filtering correct in UNION

[bnjmnnl]

Hello all, 
Maybe this is an easy take, but I'm facing some issues. I have 2 tables that together form the third table with the UNION function in DAX. Take a look at tables below:

	Table 1
row	ID	amount
1	1001	10
2	1002	10
	Table 2
row	ID	amount
1	1003	12
2	1004	15
	Table 3
row	ID	amount
1	1001	10
2	1002	10
3	1003	12
4	1004	15

However, I want the user to be able to first set filters for table 1, then for table 2, and the outcome of both tables should be displayed in table 3. But now, when I filter 1 row from table 1, table 3 also only shows that row. But when I also select a row in table 2, table 3 turns empty. 
Is the UNION function the correct one for this? Or is this a relational issue? Would be thankful for the help!

[Anonymous · Accepted solution]

Hi @bnjmnnl ,
If you want to use two filters to display the filtered results on a single table, you first need to make sure that there is no relationship between these two tables

Create a measure

Is Fittered = 
IF(
    SELECTEDVALUE('Table 3'[Row]) IN VALUES('Table 1'[Row]) || SELECTEDVALUE('Table 3'[Row]) IN VALUES('Table 2'[row]),
    1,
    0
)

Apply the measure to the Table 3

Final output

Best regards,
Albert He

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

[HotChilli]

"when I filter 1 row from table 1" - where are you doing this?