Inner Join in PowerShell (without SQL)

Question

How do we make Inner-Join or something a Cross-Join in PowerShell or PowerCLI?

Even though im new to PowerCLI/PowerShell , I do have a basic grasp on them, yet have practically spent 2 days trying to figure this, going through numerous documentations and blogs to no avail.

All I really want to know is if after typing my command

Get-Content File.txt 

and getting:

Output1 or Table1 is

Name: Abc
Group: Bad
Policy: Great

Name: redi
Group: Good 
Policy: MAD

etc. etc.

100s of these, and obviously more than just the 3 elements of Name, Group, Policy each.

---

Table2/Output2

Name: Abc
Limit: 10
used: 5

Name: redi
Limit: 20
used: 1

etc. etc.

100s of these.

---

and like 13 more of these text file tables, all with the "Name" as unique.

How can I combine it into one output at the end using Name with all the other elements?

My most obvious thought was something akin to joins, even if I had to do them 1 at a time, but even that I cant figure out how to do.

Is there anyway to do this in PowerShell itself without me having to go into Python or SQL?

If yes is there a method that is able to combine fields in spots where it's null?

If its not clear what type of result I am hoping for it will look something akin to this:

Name: Abc
Group: Bad
Policy: Great
Limit: 10
used: 5


Name: redi
Group: Good 
Policy: MAD
Limit: 20
used: 1

Answer 1

Paweł Dyl provided you a solution based on your two tables. However you probably need a generic solution where you don't have to specify each property by name yourself.

---

I would combine each table to a an array. Group the tables on the Name property using the Group-Object cmdlet. Iterate over each group and create a PsObject using the properties:

$table1 = [PSCustomObject]@{ Name = 'Abc'; Group = 'Bad'; Policy = 'Great'}, [PSCustomObject]@{ Name = 'redi'; Group = 'Good'; Policy = 'MAD'}
$table2 = [PSCustomObject]@{ Name = 'Abc'; Limit = '10'; used = '5'}, [PSCustomObject]@{ Name = 'redi'; Limit = '20'; used = '1'}

$allTables = $table1 + $table2

$allTables | group Name | Foreach {
    $properties = @{}
    $_.Group | Foreach {
        $_.PsObject.Properties | Where Name -ne 'Name' | Foreach {
            $properties +=  @{
                "$($_.Name)" = "$($_.Value)"
            }
        }
    }
    $properties += @{Name = $_.Name}
    New-Object PSObject –Property $properties
}

---

Output:

Group  : Bad
Policy : Great
Name   : Abc
Limit  : 10
used   : 5

Group  : Good
Policy : MAD
Name   : redi
Limit  : 20
used   : 1

Answer 2

You can use simple loop join as follows:

$table1 = [pscustomobject]@{Name='Abc';Group='Bad';Policy='Great'},[pscustomobject]@{Name='redi';Group='Good ';Policy='MAD'}
$table2 = [pscustomobject]@{Name='Abc';Limit=10;used=5},[pscustomobject]@{Name='redi';Limit=20;used=1}

$table1 | % { 
                foreach ($t2 in $table2) {
                    if ($_.Name -eq $t2.Name) {
                        [pscustomobject]@{Name=$_.Name;Group=$_.Group;Policy=$_.Policy;Limit=$t2.Limit;Used=$t2.Used}
                    }
                }
            }

Assuming uniqueness of keys you can also use faster, hashtable approach:

$hashed = $table1 | group Name -AsHashTable
$table2 | % {
    $matched = $hashed[$_.Name]
    if ($matched) {
        [pscustomobject]@{Name=$matched.Name;Group=$matched.Group;Policy=$matched.Policy;Limit=$_.Limit;Used=$_.Used}
    }
}

You can also use generic solution and wrap it in function. It matches records by their property names:

function Join-Records($tab1, $tab2){
    $prop1 = $tab1 | select -First 1 | % {$_.PSObject.Properties.Name} #properties from t1
    $prop2 = $tab2 | select -First 1 | % {$_.PSObject.Properties.Name} #properties from t2
    $join = $prop1 | ? {$prop2 -Contains $_}
    $unique1 = $prop1 | ?{ $join -notcontains $_}
    $unique2 = $prop2 | ?{ $join -notcontains $_}


    if ($join) {
        $tab1 | % {
            $t1 = $_
            $tab2 | % {
                $t2 = $_
                foreach ($prop in $join) {
                    if (!$t1.$prop.Equals($t2.$prop)) { return; }
                }
                $result = @{}                
                $join | % { $result.Add($_,$t1.$_) }
                $unique1 | % { $result.Add($_,$t1.$_) }
                $unique2 | % { $result.Add($_,$t2.$_) }
                [PSCustomObject]$result
            }
        }
    }
}

$table1 = [pscustomobject]@{Name='Abc';Group='Bad';Policy='Great'},
    [pscustomobject]@{Name='redi';Group='Good ';Policy='MAD'},
    [pscustomobject]@{Name='Not joined';Group='Very bad';Policy='Great'}
$table2 = [pscustomobject]@{Name='Abc';Limit=10;used=5},
    [pscustomobject]@{Name='redi';Limit=20;used=1},
    [pscustomobject]@{Name='redi';Limit=20;used=2}

#name is only common property, records joined by name
Join-Records $table1 $table2

#example2
$test1 = [pscustomobject]@{A=1;B=1;C='R1'},
    [pscustomobject]@{A=1;B=2;C='R2'},
    [pscustomobject]@{A=2;B=2;C='R3'}

$test2 = [pscustomobject]@{A=1;B=1;D='R4'},
    [pscustomobject]@{A=3;B=2;D='R5'},
    [pscustomobject]@{A=4;B=2;D='R6'}

Join-Records $test1 $test2 #joined by two common columns - A and B

You can also cascade calls:

$test1 = [pscustomobject]@{A=1;B=1;C='R1'},
    [pscustomobject]@{A=1;B=2;C='R2'},
    [pscustomobject]@{A=2;B=2;C='R3'}

$test2 = [pscustomobject]@{A=1;B=1;D='R4'},
    [pscustomobject]@{A=3;B=2;D='R5'},
    [pscustomobject]@{A=4;B=2;D='R6'}

$test3 = [pscustomobject]@{B=1;E='R7'},
    [pscustomobject]@{B=2;E='R8'},
    [pscustomobject]@{B=3;E='R9'}

#first join by common A and B, then join result by common B
Join-Records (Join-Records $test1 $test2) $test3