Modified version of a function posted to Technet, this one attempts to handle GO statements so can take auto generated SQL from SSMS.

invoke_sql.ps1

function Invoke-SQL {
    param(
        [string] $connectionString = ".\SQLEXPRESS",
        [string] $sqlCommand = $(throw "Please specify a query."),
        [hashtable] $parameters = @{},
        [switch] $splitOnGo
      )
    $queries = @()

    ## Split sqlCommand on GO keyword.
    ## GO isn't strictly proper SQL, it's a feature only honored by SSMS
    ## to break up your SQL scripts.
    if ($splitOnGo -and ($parameters.Count -gt 0)) {
        throw "Cannot execute parameterized query while splitting on GO!"
        return
    }
    if ($splitOnGo) {
        $sql_text = ($sqlCommand.Split([Environment]::NewLine) | % { $_.Trim() }) -join "`n"
        $go_pattern = New-Object System.Text.RegularExpressions.Regex ('(?i)^GO', [System.Text.RegularExpressions.RegexOptions]::Multiline)
        $queries += $go_pattern.Split($sql_text) | ? { $_ -notlike "GO" } | ? { $_ }
    }
    else {
        $queries += $sqlCommand
    }

    try {
        $connection = New-Object System.Data.SqlClient.SqlConnection ($connectionString)
        foreach ($query in $queries) {
            $command = New-Object System.Data.SqlClient.SqlCommand ($query,$connection)

            if ($parameters.Count -gt 0) {
                foreach($p in $parameters.Keys){
                    [Void] $command.Parameters.AddWithValue("@$p",$parameters[$p])
                }
            }
        
            if ($connection.State -notlike 'Open') { $connection.Open() }
            $adapter = New-Object System.Data.sqlclient.sqlDataAdapter $command
            $dataset = New-Object System.Data.DataSet
            $adapter.Fill($dataset) | Out-Null

            $dataset.Tables
        }
    }
    finally {
        if ($connection) { $connection.Close() }
    }
}