PQ - Use table to edit values of another table in Power Query

(question from the web)

Quote:

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How do we update values in Table A using the Values of Table B and keep the rest as they are?

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TABLE A						TABLE B				Result
SiteId	date	Value 1	Value 2	Value 3		SiteId	date	Value2		SiteId	date	Value 1	Value 2	Value 3
1	01/01/2020	5	20	500		1	01/01/2020	25		1	01/01/2020	5	25	500
1	02/05/2020	6	60	100		3	01/01/2021	73		1	02/05/2020	6	60	100
3	01/01/2021	2	85	250						3	01/01/2021	2	73	250
5	01/01/2020	6	14	566						5	01/01/2020	6	14	566

Code:

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let
    SourceA = Excel.CurrentWorkbook(){[Name="TableA"]}[Content],
    SourceB = Excel.CurrentWorkbook(){[Name="TableB"]}[Content],
    Join = Table.NestedJoin(SourceA, {"SiteId", "date"}, SourceB,{"SiteId", "date"}, "Table", JoinKind.LeftOuter),
    Expand = Table.ExpandTableColumn(Join, "Table", {"Value2"}, {"Value2"}),
    IF = Table.AddColumn(Expand, "Custom", each if [Value2] = null then [Value 2] else [Value2]),
    TSC = Table.SelectColumns(IF,{"SiteId", "date", "Value 1", "Custom", "Value 3"}),
    Ren = Table.RenameColumns(TSC,{{"Custom", "Value 2"}}),
    Type = Table.TransformColumnTypes(Ren,{{"date", type date}})
in
    Type

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