Using Data to create a file of original/unique entries

Hi Mr_Stern 

Here is one way, you need to take care of your manual column

output

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("jY7BCoJAEIZfZfCcoLtgelzMsDSJii7SYc1BhXUXNg18m56lJ2vXLkWXTjP/z//PN2XpsHTvLBwS0ig6m2WrWgkpSj0ZwYTosAYX9q3AyhjzVIPqu9tgpC16xPd857Io5zSXVzRuQCgl9lzWiUZphJNWo22wvhqFDUGs5KCVEKiNHbM8hxPLksPzAUcGfrgpYs+HnbuGFZ8+UOSNmp8OyJJ6lrLiPUJSSw7JHTVv8E9S8YP6Jl1e", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Payroll = _t, #"Candidate ID" = _t, WorkerName = _t, Worker_Occupation = _t, RateDescription = _t, GradeCode = _t, #"Date Added" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Payroll", type text}, {"Candidate ID", type text}, {"WorkerName", type text}, {"Worker_Occupation", type text}, {"RateDescription", type text}, {"GradeCode", type text}, {"Date Added", Int64.Type}}),
    originTable = Table.RemoveColumns(#"Changed Type",{"GradeCode"}),
    Custom1 = List.Union({ Table.ToRows( originTable), Table}),
    Custom2 = Table.FromRows(Custom1, Table.ColumnNames(originTable)),
    #"Added Custom" = Table.AddColumn(Custom2, "GradeCode", each null)
in
    #"Added Custom"

the DATA called Table

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("rVHbbsIwDP0Vq89UahLK5bFqGWWwjlHUF9SHABFUSpMppJP4G76FL1syVgSsEmOaolh2bJ9j5ywWTkp1pYTTcoJ4aizukX4/M86z3AqImVB7m+O8YGtwYbrlbGnLPIw8ZBx7vx6llmWx007eWjhvFRW6Kr8bqVgx43YwIdgijwu+kYrBXMlKm/gSrmtjC3EzVgd3iWebI1oyGKwFhcEHU3TD7gP8YoSgXFbcFkEohVaSc6ZqVGy39I0Jg8kE5sF4MDseIA0A9UZJ6CF4cZ8govuHx75Hinu3pMkP1ibSRyQkxiF+k4aN/+e3CWr6v4yuVoWgWp4XaFstyFXKTd0U5qx8/199zkx/0Ycg5FvCrDDgQkNGBQzlZmuekkrt2CXJSZXZMIHoNQ5P8JN0VOMfD/Vx8vwT", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [SourceSystem = _t, Employer_Ref = _t, Worker_Ref = _t, WorkerName = _t, Worker_Occupation = _t, PeriodCode = _t, Timesheet_Number = _t, RateDescription = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"SourceSystem", type text}, {"Employer_Ref", type text}, {"Worker_Ref", type text}, {"WorkerName", type text}, {"Worker_Occupation", type text}, {"PeriodCode", Int64.Type}, {"Timesheet_Number", Int64.Type}, {"RateDescription", type text}}),
    #"Removed Other Columns" = Table.SelectColumns(#"Changed Type",{"Employer_Ref", "Worker_Ref", "WorkerName", "Worker_Occupation",  "RateDescription","PeriodCode"}),
    #"Filtered Rows" = Table.SelectRows(#"Removed Other Columns", each ([Worker_Occupation] <> "")),
    #"Removed Duplicates" = Table.Distinct(#"Filtered Rows", {"Employer_Ref", "Worker_Ref", "WorkerName", "Worker_Occupation"}),
    Custom1 = Table.ToRows( #"Removed Duplicates")
in
    Custom1