Delete rows with a condition in PowerQuery

Hey Dani,

Thanks for the question. It's a common scenario that can be a little tricky. Here's a way: 
 

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("hZFLCsAgDETvknUFzUftWYp36LLHL65My0hcSXg4eeN10TNPoYPueeaFM0vKLbHROP4Ae+AEgESARoB5IAOgbl5gZFEEAN6iGAA+Fh0AGkVYFFGjiBZpdgeIK0pgDwYA3uwgqAevKbAHFGFRxOwBjJd9T5kXoFCuAYA/D6tXAmPd7KnwQwUAdVOFeiUa4wU=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Batch = _t, Parameter = _t, #"Inspection date" = (type date)]),
    ChType = Table.TransformColumnTypes(Source,{{"Batch", type text}, {"Parameter", type text}, {"Inspection date", type date}}),
    RowsWithNull = Table.SelectRows(ChType, each [Inspection date] = null),
    BatchesToRemove = List.Distinct( RowsWithNull[Batch] ),
    BackToSource = Source,
    RemoveRows = Table.SelectRows(BackToSource, each not List.Contains( BatchesToRemove, [Batch] ) )
in
    RemoveRows

You could try above steps. You would

1. Filter your data only the items with null

2. Retrieve the batches related to these

3. Filter the original dataset to exclude these

Cheers,

Rick

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