The move that lost the dates
A club moves its sales from an old sheet to a new system. The import finishes. Every date has changed to the wrong month.
The old system wrote day first. The new one read month first. A move is not a copy. It needs a plan: take out, prepare, change to fit, and put in.
Key words
| Word | What it means | Example |
|---|---|---|
| Extract | To take the data you need out of its source. | Pull last year's sales |
| Export | To send data out of a system as a file. | Save as a CSV file |
| Transform | To change data so it fits what the new system expects. | Day first to year first |
| Import | To load data into a system from a file. | Upload the CSV file |
| ETL | Extract, transform, load: the three main steps of moving data. | Out, change, in |
| CSV | A plain text file where commas split each line into columns. | bun,4,2 |
| Redundant data | Data you do not need to move, such as repeats. | A test row |
| Compliance | Following the law and security rules. | Keep personal data protected |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can plan and carry out a move of data from one storage system to another, in the right order.
Starter: what you already know
Have a go
Starter: what you already know
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Worked example: one line moves
| Step | The line now |
|---|---|
| Extract | 02/03/2026,bun,£2.00 and a test row |
| Prepare | The test row is removed |
| Space check | Free 100 GB, need 40 GB, keep 20 GB spare: fine |
| Export | A CSV file with the line |
| Transform | 2026-03-02, bun, 200 |
| Import | One row in the new system |
The cells students fill in are left blank in this preview.
Try it: transform one line
line = "02/03/2026,bun,£2.00"
parts = line.split(",")
date_parts = parts[0].split("/")
iso = date_parts[2] + "-" + date_parts[1] + "-" + date_parts[0]
money = parts[2].replace("£", "").split(".")
pence = int(money[0]) * 100 + int(money[1])
print(iso, parts[1], pence)
# Try it: change the line to a new date and price and press Run.
Check: the order matters
Have a go
Check: the order matters
3 questionsHave a go: your answers are marked here and then forgotten. Sign in if you would like your score kept, and to pick up where you left off.Sign in to keep your score
Your answers are marked here and are not kept. A college account keeps every student’s marks.