Iain-pwsh.org-112018-2.ps1

Function Recover-LogSpace
{
    [CmdletBinding()]
    Param(
        [parameter(ParameterSetName='Multiple')]
        [parameter(ValueFromPipelineByPropertyName=$true,
            ParameterSetName='Single')]
        [string[]]$SqlServer,

        [parameter(ValueFromPipelineByPropertyName=$true,
            ParameterSetName='Single')]
        [string[]]$Database
    )

    PROCESS {
        foreach($server in $SqlServer) {
            "Connecting to $server"
            if($Database) {
                "Working on database $Database"
            }
            else {
                "Working on all databases on server"
            }
        }
    }
}

[PSCustomObject]@{
    SqlServer = "sqlserver1\instance"
} | Recover-LogSpace

[PSCustomObject]@{
    SqlServer = "sqlserver1\instance"
    Database  = "database1"
},
[PSCustomObject]@{
    SqlServer = "sqlserver2\instance"
    Database  = "database2"
} | Recover-LogSpace 

### Output

Connecting to sqlserver1\instance
Working on all databases on server
Connecting to sqlserver1\instance
Working on database database1
Connecting to sqlserver2\instance
Working on database database2