There is a data table:

Now we want to concatenate the ID numbers for each group of names by | to form a string, and put the result in column C (calculate in cell C1):

=spl("=E(?1).new(cum(~~+""|""+ID;Name):IDs)",A1:B13)

esProc Desktop and Excel Processing
7.12 Merge data of the same group
7.14 Calculate proportion using aggregation information of data of the same group