Merge two CSV files while adding new and overwriting existing entries

Question

I have a configuration.csv that holds a template data like this:

| path       | item  | value  | type |
|------------|-------|--------|------|
| some/path  | item1 | value1 | ALL  |
| some/path  | item2 | UPDATE | ALL  |
| other/path | item1 | value2 | SOME |

and customization.csv that has service specific configuration:

| path       | item  | value  | type |
|------------|-------|--------|------|
| some/path  | item2 | value3 | ALL  |
| new/path   | item3 | value3 | SOME |

My goal is to merge them and end up with something like this:

| path       | item  | value  | type |
|------------|-------|--------|------|
| some/path  | item1 | value1 | ALL  |
| some/path  | item2 | value3 | ALL  |
| other/path | item1 | value2 | SOME |
| new/path   | item3 | value3 | SOME |

This should add any new entries and update any existing ones. No one column can be used for unique identification - both path and item needs to be combined, as they are guaranteed to be unique.

Answer 1

I suggest to use Compare-Object and as the values from customization.csv shall persist use this files values as -ReferenceObject

## Q:\Test\2019\03\01\SO_54948111.ps1

$conf = Import-Csv '.\configuration.csv'
$cust = Import-Csv '.\customization.csv'

$NewData = Compare-Object -ref $cust -diff $conf -Property path,item -PassThru -IncludeEqual|
    Select-Object -Property * -ExcludeProperty SideIndicator

$NewData
$NewData |Export-Csv '.\NewData.csv' -NoTypeInformation

Sample output

> Q:\Test\2019\03\01\SO_54948111.ps1

path       item  value  type
----       ----  -----  ----
some/path  item2 value3 ALL
some/path  item1 value1 ALL
other/path item1 value2 SOME
new/path   item3 value3 SOME