CODEWITHSUNDEEP
powershellhashduplicateshaving
m1ghtyBear
m1ghtyBear

Reputation: 11

How to find duplicate values in powershell hash

Imagine the following hash: 

$h=@{}
$h.Add(1,'a')
$h.Add(2,'b')
$h.Add(3,'c')
$h.Add(4,'d')
$h.Add(5,'a')
$h.Add(6,'c')

What query would return the 2 duplicate values 'a' and 'c' ?

Basically I am looking for the powershell equivalent of the following SQL query (assuming the table h(c1,c2):

select c1
from h 
group by c1
having count(*) > 1

Upvotes: 1

Views: 8167

Answers (3)

iRon
iRon

Reputation: 23713

Just a slightly different question:

How to list the duplicate items of a PowerShell Array

But a similar solution as from Frode F:

$Duplicates = $Array | Group | ? {$_.Count -gt 1} | Select -ExpandProperty Name

Upvotes: 1

mjolinor
mjolinor

Reputation: 68303

You can use another hash table:

$h=@{}
$h.Add(1,'a')
$h.Add(2,'b')
$h.Add(3,'c')
$h.Add(4,'d')
$h.Add(5,'a')
$h.Add(6,'c')

$h1=@{}
$h.GetEnumerator() | foreach { $h1[$_.Value] += @($_.name) }
$h1.GetEnumerator() | where { $_.value.count -gt 1}

Name                           Value                                                                                                  
----                           -----                                                                                                  
c                              {6, 3}                                                                                                 
a                              {5, 1}

Upvotes: 1

Frode F.
Frode F.

Reputation: 54891

You could try this:

$h.GetEnumerator() | Group-Object Value | ? { $_.Count -gt 1 }

Count Name Group                                                                   
----- ---- -----                                                                   
    2 c    {System.Collections.DictionaryEntry, System.Collections.DictionaryEntry}
    2 a    {System.Collections.DictionaryEntry, System.Collections.DictionaryEntry}

If you store the results, you could dig into the group to get the key-name for the duplicate entries. Ex.

$a = $h.GetEnumerator() | Group-Object Value | ? { $_.Count -gt 1 }

#Check the first group(the one with 'c' as value)
$a[0].Group

Name Value
---- -----
6    c    
3    c

Upvotes: 9

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