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8. Adding Columns: Power Query Add Column Tab and DAX Calculated Columns

8.7 Duplicate Column

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In short: Duplicate Column copies a column; then transform the copy without touching the original.

Start with a problem

Ravina wants to keep Order Date and also have a Month column derived from it.

Explain simply

Duplicate Column copies a column; then transform the copy without touching the original.

Show the data

Order ID Order Date
301 06-Apr-2026
304 04-May-2026

About this data: This table uses columns: Order ID, Order Date. This table uses columns: Order ID, Order Date, Month. This table uses columns: Wrong result, Reason, Correction. Values shown are the lesson examples already on this page (not a new dataset).

Fictional sample data. Practice file: visuals_orders_apr_may_2026.csv (source: src/practice/).

Demonstrate

  1. Select Order Date › Add Column › Duplicate Column.

    Your result should look like this:

    Columns
    Order Date, Order Date - Copy

  2. Select the copy › Transform › Date › Month › Name of Month; rename Month.

    Your result should look like this:

    Month
    April, May

Show the result

Your result should look like this (fictional sample):

Order ID Order Date Month
301 06-Apr-2026 April
304 04-May-2026 May

Explain what happened

The copy was transformed in place; the original stays a date.

Explore further

  • Add Column › Date › Month Name does the same in one step.

Detailed reference for this lesson:

Add Column › Duplicate Column copies the selected column as Column - Copy. Use it before a destructive change when you still need the original, for example duplicate Order DateTime and then turn the copy into Order Hour with Transform › Time › Hour.

Ravindra Bagale's Tip

Friends, many students duplicate a column to "keep a backup" and then load both into the model. If you duplicate a column to transform it, remove the original (or the copy) before loading so the model doesn't carry the same data twice. It's very simple – just make it a habit.

Fix common mistakes

Wrong result Reason Correction
Original became text Transformed the original Transform the copy
Month sorts alphabetically Text month Add Month Number or use a Date table
Many copies in model Copies never removed Remove or hide

Practise independently

Practice task

How many orders in the visuals file have Month = May?

Hints
  • 304–308.
Solution

5.

Think like a professional

Month columns belong in the Date table in a real model (Module 11.5).

Ravi Sir's Cards for this lesson

Duplicate Column. Some changes replace a column. Sometimes you still need the original.Revision card

मराठी cards