Iain-pwsh.org-112018.ps1

function Recover-LogSpace {
    [CmdletBinding()]
    Param(
        [parameter(ValueFromPipelineByPropertyName,
                   Mandatory)]
        [string[]]
        $SqlServer,

        [parameter(ValueFromPipelineByPropertyName)]
        [string[]]
        $Database
    )

    process {
        "Working on $SqlServer"

        if ($Database) {
            "Connecting to $Database"
        } else {
            "Connecting to all databases"
        }
    }
}

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

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

### Output

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