Powershell, Modify CSV field based on other field in same CSV - arrays

Question

I'm stuck trying to find a better way of modifying large (1000+ rows) CSV file than multiple foreach loops.
I have a CSV file with:
Name,login,ID,MGRID,MGRNAME
Bob Smith,bsmith,101,201,Drake Suzy
Suzy Drake,sdrake,201,300,Long Jane
John Bass,jbass,102,201,Drake Suzy
Jane Long,jlong,300,300,Long Jane
I'm trying to find the best way to import the csv and then set the MGRNAME for each employee to match the login of the corresponding MGR. I'd like to see:
Name,login,ID,MGRID,MGRNAME
Bob Smith,bsmith,101,201,sdrake
Suzy Drake,sdrake,201,300,jlong
John Bass,jbass,102,201,sdrake
Jane Long,jlong,300,300,jlong
I've tried importing the csv and then replacing the MGRNAME using:
$Sup = Import-Csv $Csvfile
Foreach ($MGR in $SUP){
$SUP1 = $MGR.MGRId
$SupID = ($sup | Where-Object {$_.login -eq $Sup1}).Login
Foreach ($ID in $Sup) {
($Sup | Where-Object {$_.MGRID -eq $SupID}).MGRNAME = $supId
}
}
I've also tried using something like:
$Users = Import-Csv $Csvfile
Foreach ($MGR in $users){
$supID=$MGR.MGRID
$RowIndex=[array]::Indexof($MGR.MGR.NAME,"$supID")
}
Any helpful suggestions welcome.
Thank you

Answer 1

here's one way to get the job done. [grin] what it does ...
fakes reading in a CSV
when ready to do this with real data, replace the entire #region/#endregion with a call to Import-Csv.
iterates thru the imported list
if the current user ID is the same as the MgrId, set the MgrName to the current login
otherwise, look up the Mgr with a .Where({}) method call with the mode set to First & set the MgrName with the resulting login
shows the result
the .Where({}) lookup could be slow if the import is large. if so, you likely otta replace that with a hashtable for lookups. however, premature optimization is bad coding, so i did not do that. [grin]
also, the export to CSV seems well documented, so i did not include that.
the code ...
#region >>> fake reading in a CSV file
# in real life, use Import-CSV
$UserList = #'
Name,login,ID,MGRID,MGRNAME
Bob Smith,bsmith,101,201,Drake Suzy
Suzy Drake,sdrake,201,300,Long Jane
John Bass,jbass,102,201,Drake Suzy
Jane Long,jlong,300,300,Long Jane
'# | ConvertFrom-Csv
#endregion >>> fake reading in a CSV file
foreach ($UL_Item in $UserList)
{
if ($UL_Item.Id -eq $UL_Item.MgrId)
{
$UL_Item.MgrName = $UL_Item.Login
}
else
{
$UL_Item.MgrName = $UserList.Where({$_.Id -eq $UL_Item.MgrId}, 'First', 1).Login
}
}
$UserList |
# remember - DO NOT use the "Format-*" cmdlets for anything other than _final output as plain text_ [*grin*]
Format-Table
the output ...
Name login ID MGRID MGRNAME
---- ----- -- ----- -------
Bob Smith bsmith 101 201 sdrake
Suzy Drake sdrake 201 300 jlong
John Bass jbass 102 201 sdrake
Jane Long jlong 300 300 jlong

Answer 2

Joining objects is a quite common activity in PowerShell, therefore I have created a 'Join-Object' cmdlet sometime ago which I still maintaining by adding features along with using a hashtable (for performance reasons as #Lee_Dailey mentiones) and adding self-join capabilities:
InnerJoin $UserList -on MgrId -eq id -discern '',MGR |
Select-Object Name, Login, ID, MGRID, MGRLogin | Format-Table
Name login ID MGRID MGRlogin
---- ----- -- ----- --------
Bob Smith bsmith 101 201 sdrake
Suzy Drake sdrake 201 300 jlong
John Bass jbass 102 201 sdrake
Jane Long jlong 300 300 jlong
Note that the column header MGRLogin doesn't exactly match the example in your question (which is actually inconsistent with the employee Name and - Login headers), but if you really want the same header you might do:
InnerJoin $UserList -on MgrId -eq id -discern '',MGR |
Select-Object Name, Login, ID, MGRID, #{n='MGRName'; e={$_.MGRLogin}} | Format-Table
For more details, see the embedded help (Help Join-Object) and In Powershell, what's the best way to join two tables into one?