Get rows from one datatable where Id not in another using Powershell - powershell

Question

I have two DataTables in Powershell with differing columns but one common Id column.
I want to get the rows from DataTable A where the Id of the row doesn't appear in DataTable B.
|DataTable A |
|---------------------------|
|Id|SomeName|SomeDescription|
|--|--------|---------------|
|1 |Blah |Whatevs |
|2 |Foo |Bar |
|3 |Woo |Yeah |
|DataTable B |
|------------------------------------|
| Id | SomeOtherName | SomeOtherDesc |
|----|---------------|---------------|
| 1 | Blah blah | Yadda yadda |
| 2 | Foo foo | Bah bah |
The result I'd like:
|DataTable Result |
|---------------------------|
|Id|SomeName|SomeDescription|
|--|--------|---------------|
|3 |Woo |Yeah |
How is this best done in Powershell?

Answer 1

Quickly whipped a csv table and not a data table, but if the ID columns are put in an array, this should work,:
$tableA = #'
Id,somename,somedescription
1,Blah,Whatevs
2,Foo,Bar
3,Woo,Yeah
'#
$tableB = #'
Id,somename,somedescription
1,Blah,Whatevs asd
2,Foo,Bar asd
'#
$importA = $tableA | Convertfrom-csv
$importB = $tableB | Convertfrom-csv
$importA | Where-Object { $importB.Id -notcontains $_.Id }

Answer 2

Since you work with DataTables and the result should also be a DataTable, this should do it:
# DataTable A
$dtA = New-Object System.Data.DataTable
$dtA.Columns.Add([System.Data.DataColumn]::new("Id",[int]))
$dtA.Columns.Add([System.Data.DataColumn]::new("SomeName"))
$dtA.Columns.Add([System.Data.DataColumn]::new("SomeDescription"))
$row = $dtA.NewRow()
$row["Id"] = 1
$row["SomeName"] = "Blah"
$row["SomeDescription"] = "Whatevs"
$dtA.rows.Add($row)
$row = $dtA.NewRow()
$row["Id"] = 2
$row["SomeName"] = "Foo"
$row["SomeDescription"] = "Bar"
$dtA.rows.Add($row)
$row = $dtA.NewRow()
$row["Id"] = 3
$row["SomeName"] = "Woo"
$row["SomeDescription"] = "Yeah"
$dtA.rows.Add($row)
# DataTable B
$dtB = New-Object System.Data.DataTable
$dtB.Columns.Add([System.Data.DataColumn]::new("Id",[int]))
$dtB.Columns.Add([System.Data.DataColumn]::new("SomeOtherName"))
$dtB.Columns.Add([System.Data.DataColumn]::new("SomeOtherDesc"))
$row = $dtB.NewRow()
$row["Id"] = 1
$row["SomeOtherName"] = "Blah blah"
$row["SomeOtherDesc"] = "Yadda yadda"
$dtB.rows.Add($row)
$row = $dtB.NewRow()
$row["Id"] = 2
$row["SomeOtherName"] = "Foo foo"
$row["SomeOtherDesc"] = "Ba ba"
$dtB.rows.Add($row)
# create a clone of datatable A (no data, just the structure)
$dtResult = $dtA.Clone()
# Get the Id values that are in DataTable A, but not in DataTable B
$diff = Compare-Object -ReferenceObject $dtA.Id -DifferenceObject $dtB.Id -PassThru | Where-Object { $_.SideIndicator -eq '<=' }
$dtA | Where-Object { $diff -contains $_.Id } | ForEach-Object {
# here, $_ is of type System.Data.DataRow
# you cannot add this DataRow directly because it belongs to another DataTable,
# to overcome that use the 'ItemArray' property to get an array of the values inside
$null = $dtResult.Rows.Add($_.ItemArray)
}
$dtResult
Result (type System.Data.DataTable):
Id SomeName SomeDescription
-- -------- ---------------
3 Woo Yeah