Check if Two Values in Array / Data Table match - powershell

Question

I put this question on here before, but I missed an important detail which causes huge issue. There will be duplicate account numbers. So I'm doing it by current_read_date now to avoid duplicates in account number. To ensure values being added to $accounts are new from the CSV.
I am trying to get all the accounts from $f which do not match the accounts in $table4 into $accounts. But I need to also check if the current_read_date matches or not.
CSV into Array $f:
Account_no |occupant_code|current_read_date
-----------|-------------|-----------------
12345 | 1 | 7/17/2017 15:32:00 AM
67890 | 2 | 7/17/2017 12:00:00 AM
45678 | 3 | 7/17/2017 12:00:00 AM
DataTable $table4
Account_no |occupant_code|current_read_date
-----------|-------------|-----------------
12345 | 1 | 7/17/2017 12:00:00 AM
12345 | 1 | 7/17/2017 15:32:00 AM
67890 | 1 | 7/17/2017 13:00:00 AM
67890 | 1 | 7/17/2017 22:00:00 AM
45678 | 3 | 7/17/2017 12:00:00 AM
Desired result:
$accounts =
67890 | 2 | 7/17/2017 12:00:00 AM
Current code:
$accounts = Import-Csv $f |
select account_no, current_read_date |
where { $table4.account_no -notcontains $_.account_no }
What this needs to do is to check that current_read_date doesn't match, i.e.:
12345: account and date from $f and $table4 match; so it's ignored
67890: account matches $table4, but the current_read_date does not match, so it is a new value, thus it is added to $accounts.
I believe I need to use Group-Object, but I do not know how to use that correctly.
I tried:
Import-Csv $f |
select account_no, occupant_code |
Group-Object account_no |
Where-Object { $_.Group.current_read_date -notcontains $table4.current_read_date }
This is the previous question:
How to use Group-Object on this?
All the answers here failed because I forgot to provide the information that account_no is not unique; there will be frequent duplicates.
All assistance would be greatly appreciated, I've been stuck on this for awhile.
I've also tried this
$testList = #()
$testList = Import-Csv $f | select account_no, occupant_code, current_read_date, current_reading
$accounts = new-object System.Collections.ArrayList
$testSet = $table4
foreach($myThing in $testList)
{
if($myThing.account_no -in $testSet.account_no )
{
foreach($ts in $testSet)
{
if ($myThing.account_no -match $ts.account_no -and $myThing.occupant_code -match $ts.occupant_code)
{
$ts.account_no
$ts.occupant_code
}
else {
$accounts.add($myThing) | out-null
write-host $mything
}
}
}
This fails because it goes through each number, therefore, 12345 will be checked against 67890, and will added 12345 to the $accounts list, even though it already exists, because I cannot compare each individually at a time with table4.
Thanks

Answer 1

$accounts = $f | Where {
$Record = $_
$AccNo = $table4 | Where {$_.Account_no -eq $Record.Account_no}
!($AccNo | Where {$_.current_read_date -eq $Record.current_read_date})
}
$accounts | Format-Table
Result:
Account_no occupant_code current_read_date
---------- ------------- -----------------
67890 2 7/17/2017 12:00:00 AM

Answer 2

Build a reference list from the records in $table4
$ref = $table4 | ForEach-Object {
$_.Account_no, $_.occupant_code, $_.current_read_date -join ','
}
then filter the records from $f by that reference list:
$accounts = Import-Csv $f | Where-Object {
$ref -notcontains ($_.Account_no, $_.occupant_code, $_.current_read_date -join ',')
} | Select-Object -Expand Account_no -Unique