Help With Transforming Table to Show Unique Records

Hi frozenovergen 

You could do this in the Query Editor if you wanted.
Create a copy of the full table.

Then another copy with the date removed and duplicates removed.

Join the two together using MERGE

Then expand the data and choose AGGREGATE the Date Min and MAX

Here is the M code for the full table

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WckksSVXSUXIsLk4tAdI++cXFCiGVBSCxoNTE4vw85/zc3NS8kmKlWJ1oJSNzfQNzfSMDIxMFAwMrAwOYTgVHIMslvzyvJDMXpLWisgq/eicc6s1INB+XelzmmxJnfmJSMn71TjjUm5BoPi71uMw3JjF8cKnHFT5GJJqPSz0282MB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t, Column3 = _t, Column4 = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}, {"Column2", type text}, {"Column3", type text}, {"Column4", type text}}),
#"Promoted Headers" = Table.PromoteHeaders(#"Changed Type", [PromoteAllScalars=true]),
#"Changed Type1" = Table.TransformColumnTypes(#"Promoted Headers",{{"Date", type datetime}, {"Asset", type text}, {"Loss Type", type text}, {"ReasonComments", type text}})
in
#"Changed Type1"

And here is the code for the aggregate table

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WckksSVXSUXIsLk4tAdI++cXFCiGVBSCxoNTE4vw85/zc3NS8kmKlWJ1oJSNzfQNzfSMDIxMFAwMrAwOYTgVHIMslvzyvJDMXpLWisgq/eicc6s1INB+XelzmmxJnfmJSMn71TjjUm5BoPi71uMw3JjF8cKnHFT5GJJqPSz0282MB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t, Column3 = _t, Column4 = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}, {"Column2", type text}, {"Column3", type text}, {"Column4", type text}}),
#"Promoted Headers" = Table.PromoteHeaders(#"Changed Type", [PromoteAllScalars=true]),
#"Changed Type1" = Table.TransformColumnTypes(#"Promoted Headers",{{"Date", type datetime}, {"Asset", type text}, {"Loss Type", type text}, {"ReasonComments", type text}}),
#"Removed Columns" = Table.RemoveColumns(#"Changed Type1",{"Date"}),
#"Removed Duplicates" = Table.Distinct(#"Removed Columns"),
#"Reordered Columns" = Table.ReorderColumns(#"Removed Duplicates",{"Asset", "ReasonComments", "Loss Type"}),
#"Merged Queries" = Table.NestedJoin(#"Reordered Columns", {"Asset", "ReasonComments"}, #"Full Table", {"Asset", "ReasonComments"}, "Full Table", JoinKind.LeftOuter),
#"Aggregated Full Table" = Table.AggregateTableColumn(#"Merged Queries", "Full Table", {{"Date", List.Min, "Min of Date"}, {"Date", List.Max, "Max of Date"}})
in
#"Aggregated Full Table"

If you want to load the whole table in instead.

I don't think you need DAX, just drag the 3 categories in and use Min and MAX on the dates: