Calculate duration with start and end date in two tables

[mcflurry]

I'm trying to calculate duration with two columns from two tables.

I've tried adding a column in one of the tables with this code:

Duration = ('Started'[Start Time] - RELATED(Completed[End Time]))

But it gives an error:

"A single value for column 'Start Time' in table 'Started' cannot be determined. This can happen when a measure formula refers to a column that contains many values without specifying an aggregation such as min, max, count, or sum to get a single result."

I've tried DATEDIFF too, but i can only pick columns from one of the tables, can't use two tables.

Any suggestion?

[johnt75]

Try SELECTEDVALUE()

Duration = DATEDIFF( SELECTEDVALUE('Started'[Start Time]), SELECTEDVALUE( 'Completed'[End Time]), MINUTE )

[Syk]

Try something like this...

Duration = DATEDIFF(MAX('Started'[Start Time]),MAX(Completed[End Time]),MINUTE)

[mcflurry]

It "works", it justs displays the same result for every row.

[Syk]

What's the relationship between the two tables?

[mcflurry · Accepted solution]

A column called "ID".

OK

Finally got it with this:

Duration = DATEDIFF(MAXX(RELATEDTABLE(Started),'Started'[Start Time]),Completed[End Time],MINUTE)