PowerShell - List all SQL instances on my system?

Question

Is there a Powershell command to list all SQL instances on my system? (MS SQL 2008)

Answer 1

This function it gonna return all the installed instances with the version details in a object list:

function ListSQLInstances {
$listinstances = New-Object System.Collections.ArrayList
$installedInstances = (get-itemproperty 'HKLM:\SOFTWARE\Microsoft\Microsoft SQL Server').InstalledInstances
foreach ($i in $installedInstances) {
    $instancefullname = (Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL').$i
    $productversion = (Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Microsoft SQL Server\$instancefullname\Setup").Version
    $majorversion = switch -Regex ($productversion) {
        '8' { 'SQL2000' }
        '9' { 'SQL2005' }
        '10.0' { 'SQL2008' }
        '10.5' { 'SQL2008 R2' }
        '11' { 'SQL2012' }
        '12' { 'SQL2014' }
        '13' { 'SQL2016' }    
        '14' { 'SQL2017' } 
        '15' { 'SQL2019' } 
        default { "Unknown" }
    }
    $instance = [PSCustomObject]@{
        Instance             = $i
        InstanceNameFullName = $instancefullname;
        Edition              = (Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Microsoft SQL Server\$instancefullname\Setup").Edition;
        ProductVersion       = $productversion;
        MajorVersion         = $majorversion;
    }
    $listinstances.Add($instance)
}

Return $listinstances
}

$instances = ListSQLInstances
foreach ($instance in $instances) {
    Write-Host $instance.Instance
}