Jorge Solá 10/21/2016 7:44:27 AM
I've implemented a workaround solution. I'm aware it only works in a particular case, but just in case it might help you, here it is:
Let's say you want to have a summary column with a concatenate of [Column A] unique values.
1) Create in the Master table a [Concatenate with repeated values] summary column of [Column A], with space-separated values.
2) In the Details table create a [Lookup Concatenate with repeated values] column that will read the values in the column you just created in the Master table.
3) In the Details table create a [Unique Column A values] column that has an initial value formula like:
If(Contains([Lookup Concatenate with repeated values], [Column A]), "", [Column A])
In other words, when a new Details record is created, this column will be blank if the value in [Column A] in the new record is a repetition of the value of [Column A] in another record.
4) Now you can create in the Master table a [Concatenate with unique values] summary column of the [Unique Column A values] column. Add a filter so that the only records added to the summary are those where [Unique Column A values] is not blank.
The crucial step is 3), because if there are going to be changes to [Column A] after the record has been created, then the initial value formula will not be effective. But if the value in [Column A] is not going to change, then it will work.