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
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
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}
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
