Find Max date and return corresponding row data power query

Hi Anno2019 

You could add a grouped index onto your purchase and survey table, which could then be used as a filter to identify the most recent entry per customer. See sample code below:

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45Wci4tLsnPTS1SMFTSUTIy1Tcw1jcyMAJxgkvyi1KBwrE6SKqMQKrM9Q1M8KoCSRgCzTJFVWWEqQpkowWqKmNMGw2N9A0MUVWZKMXGAgA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Customer ID" = _t, #"Purchase Date" = _t, #"Store Name" = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Customer ID", type text}, {"Purchase Date", type date}, {"Store Name", type text}}),
#"Sorted Rows" = Table.Sort(#"Changed Type",{{"Purchase Date", Order.Descending}}),
#"Grouped Rows" = Table.Group(#"Sorted Rows", {"Customer ID"}, {{"Count", each _, type table [Customer ID=nullable text, Purchase Date=nullable date, Store Name=nullable text]}}),
#"Added Custom" = Table.AddColumn(#"Grouped Rows", "Custom", each Table.AddIndexColumn([Count],"Purchase Index",1)),
#"Expanded Custom" = Table.ExpandTableColumn(#"Added Custom", "Custom", {"Customer ID", "Purchase Date", "Store Name", "Purchase Index"}, {"Customer ID.1", "Purchase Date", "Store Name", "Purchase Index"}),
#"Removed Other Columns" = Table.SelectColumns(#"Expanded Custom",{"Customer ID", "Purchase Date", "Store Name", "Purchase Index"}),
#"Filtered Rows" = Table.SelectRows(#"Removed Other Columns", each ([Purchase Index] = 1))
in
#"Filtered Rows"

This is based on the following blog post if you want to work through the steps yourself.

Create Row Number for Each Group in Power BI using Power Query - RADACAD

If this post helps then please consider Accept it as the solution to help the other members find it more quickly.