Selecting data from multiple columns

Select[AnyTrue  @ NumberQ] @ dataset

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You said that your dataset had over 300 columns, so perhaps the following dataset is a bit more representative:

SeedRandom[2];
dataset = Dataset @ Table[
    AssociationThread[{"a","b","c","d","e"}, RandomChoice[Range[2]~Join~{"-",u,v,w,x,y,z}, 5]],
    {10}
]

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Then, if you want to select rows where there's a number in columns a, b or c, you can do the following:

With[{slots = Slot/@{"a","b","c"}},
    dataset[Select[AnyTrue[slots, NumberQ]&]]
]

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