Extract differences of CSV files into a seperate file - powershell

Question

I have a CSV file (with headers) filled with assortment data. The file will be updated once every day. I need to find the differences in those files (the old and the new one) and extract them into a separate file.
For instance: in the old file there could be a price of "18,50" and now it's an updated one of "17,90". The script should now extract this row into a new file.
So far, I was able to import both CSV files (via Import-Csv) but my current solution is to compare each row by findstr.
The problems are:
In 9 of 10 cases the strings are too long to compare.
What if a new row will be inserted - I guess the comparison wouldn't work any longer if the row isn't inserted at the end of the file.
My current code is:
foreach ($oldData in (Import-Csv $PSScriptRoot\old.csv -Delimiter ";" -Encoding "default")) {
foreach ($newData in (Import-Csv $PSScriptRoot\new.csv -Delimiter ";" -Encoding "default")) {
findstr.exe /v /c:$oldData $newData > $PSScriptRoot\diff.txt
}
}

Answer 1

Read both files into separate variables and use Compare-Object for the comparison:
$fields = 'idArtikel', 'Preis', ...
$csv1 = Import-Csv $PSScriptRoot\old.csv -Delimiter ';'
$csv2 = Import-Csv $PSScriptRoot\new.csv -Delimiter ';'
Compare-Object -ReferenceObject $csv1 -DifferenceObject $csv2 -Property $fields -PassThru | Where-Object {
$_.SideIndicator -eq '=>'
} | Select-Object $fields | Export-Csv 'C:\path\to\diff.csv' -Delimiter ';'

Answer 2

$csv1 | Join $csv2 idArtikel -Merge {$Right.$_} | Export-CSV 'C:\path\to\diff.csv' -Delimiter ';'
For details on Join (Join-Object), see: https://stackoverflow.com/a/45483110/1701026