Comments

// This is a comment

Simple example


let
    x = 1 + 1,
    y = 2 + 2,
    z = y + 1
in
    x + y + z

Another example


let Orders = Table.FromRecords({  
    [OrderID = 1, CustomerID = 1, Item = "fishing rod", Price = 100.0],  
    [OrderID = 2, CustomerID = 1, Item = "1 lb. worms", Price = 5.0],  
    [OrderID = 3, CustomerID = 2, Item = "fishing net", Price = 25.0]}),  
    #"Capitalized Each Word" = Table.TransformColumns(Orders, {"Item", Text.Proper})  
in  
    #"Capitalized Each Word"

Full example


    let
    Source = Sales,
    LookupTable = #table(
    type table
        [
            #"FROM"=text,
            #"TO"=text
        ], 
        {
            {"CEE","Central & Eastern Europe"},
            {"WE","Western Europe"}  
        }
    ),

    JT = Table.NestedJoin(
        Source, 
        {"Area"}, 
        LookupTable, 
        {"FROM"}, 
        "Map", 
        JoinKind.LeftOuter
    ),

    #"Expanded Map" = Table.ExpandTableColumn(
        JT, 
        "Map", 
        {"TO"}, 
        {"TO"}
    ),

    #"Replace non-matches with original value" = Table.AddColumn(
        #"Expanded Map", 
        "Replaced", 
        each 
            if [TO] = null then [Area] 
            else [TO]
    ),

    #"Remove original column" = Table.RemoveColumns(
        #"Replace non-matches with original value",
        {"Area", "TO"}
    ),

    #"Renamed replace column to original name" = Table.RenameColumns(
        #"Remove original column",
        {{"Replaced", "Area"}}
    )

in
    #"Renamed replace column to original name"