Multiple joins with F# SqlProvider

Query.fs

let getXsd id =
    query {
        for messageItem in ctx.ProtoType.MessageType do
        for originalMessage in messageItem.``ProtoType.OriginalMessage by Id`` do
        for messageType in originalMessage.``ProtoType.MessageType by Id`` do
        where (messageItem.Id = id)
        select (messageType.Xsd)
    } |> Seq.head