Power Query M Language
Master Course

let
    A = 10,
    B = 20,
    Total = A + B
in
    Total // Output: 30

let
    A = 10,
    B = 20,
    C = A + B,
    UnusedCalculation = Number.Power(999, 99) // Engine skips this completely!
in
    C // Output: 30

let
    Revenue = 250000,
    Cost = 175000,
    GrossProfit = Revenue - Cost,
    MarginPercentage = (GrossProfit / Revenue) * 100
in
    MarginPercentage // Output: 30%

let
    SalesAmount = 65000,
    Tier = 
        if SalesAmount >= 100000 then "Platinum Tier"
        else if SalesAmount >= 50000 then "Gold Tier"
        else if SalesAmount >= 20000 then "Silver Tier"
        else "Bronze Tier"
in
    Tier // Output: "Gold Tier"

let
    Employee = [
        EmpID = 101,
        FullName = "Rahul Sharma",
        City = "Pune",
        Salary = 65000
    ],
    SelectedCity = Employee[City] // Output: "Pune"
in
    SelectedCity

let
    TypedSales = #table(
        type table [OrderID = Int64.Type, Customer = text, Amount = number],
        {
            {1001, "Acme Corp", 45000},
            {1002, "Global Tech", 28000}
        }
    )
in
    TypedSales

let
    TotalUnits = 145,
    BoxSize = 12,
    FullBoxes = Number.IntegerDivide(TotalUnits, BoxSize), // 12 Boxes
    RemainingUnits = Number.Mod(TotalUnits, BoxSize)       // 1 Loose Unit
in
    [Boxes = FullBoxes, Loose = RemainingUnits]

let
    InvoiceDate = #date(2026, 9, 1),
    CreditDays = 45,
    DueDate = Date.AddDays(InvoiceDate, CreditDays), // #date(2026, 10, 16)
    Today = DateTime.Date(DateTime.LocalNow()),
    DaysOverdue = Duration.Days(Today - DueDate)
in
    DaysOverdue

#"Added Custom" = Table.AddColumn(
    Source, 
    "TotalCost", 
    each [Quantity] * [UnitPrice], 
    type number
)

let
    fxCalculateGST = (taxableAmount as number, gstRate as number) as record =>
        let
            tax = taxableAmount * (gstRate / 100),
            total = taxableAmount + tax
        in
            [TaxAmount = tax, InvoiceTotal = total]
in
    fxCalculateGST(10000, 18) // Output: [TaxAmount=1800, InvoiceTotal=11800]

let
    DirtyValue = "CorruptText",
    SafeNumber = try Number.From(DirtyValue) otherwise 0
in
    SafeNumber // Output: 0 (No crash!)

#"Filled Down" = Table.FillDown(Source, {"Department", "ManagerName"})

let
    Merged = Table.NestedJoin(
        Customers, {"CustomerID"}, 
        Orders, {"CustomerID"}, 
        "OrdersSubTable", 
        JoinKind.LeftOuter
    ),
    Expanded = Table.ExpandTableColumn(
        Merged, 
        "OrdersSubTable", 
        {"OrderID", "Amount"}, 
        {"OrderID", "Amount"}
    )
in
    Expanded

#"Grouped Region" = Table.Group(
    Source, 
    {"Region"}, 
    {
        {"TotalSales", each List.Sum([SalesAmount]), type number},
        {"OrderCount", each Table.RowCount(_), Int64.Type},
        {"AverageTicket", each List.Average([SalesAmount]), type number}
    }
)

#"Unpivoted Other" = Table.UnpivotOtherColumns(
    Source, 
    {"ProductID", "ProductName"}, 
    "MonthName", 
    "SalesRevenue"
)

let
    Source = Folder.Files("C:\MonthlyBranchReports\"),
    Filtered = Table.SelectRows(Source, each [Extension] = ".xlsx" and not Text.StartsWith([Name], "~$")),
    Extracted = Table.AddColumn(Filtered, "Data", each Excel.Workbook([Content], true){[Item="Sales", Kind="Table"]}[Data], type table),
    Selected = Table.SelectColumns(Extracted, {"Name", "Data"}),
    Expanded = Table.ExpandTableColumn(Selected, "Data", {"InvoiceID", "Customer", "Amount"}, {"InvoiceID", "Customer", "Amount"})
in
    Expanded