← VCE Data Analytics U3O1

Removing duplicate rows

A spreadsheet tool that deletes rows repeating the same values in the columns you choose to compare, keeping the first match. Always keep a copy of the raw data first.

Part of: VCE Data Analytics - U3O1 - Data Analytics — Module 75, ACARA Digital Technologies Years 7–8 — Acquiring and Storing Data — Module 59, ACARA Digital Technologies Years 9–10 — Acquiring and Validating Data — Module 97

Understanding Removing duplicate rows in VCE Data Analytics U3O1

What it does: Copying the sheet first keeps the raw data safe, because Remove Duplicates permanently deletes rows. Ticking all columns means a row is only removed when every value matches an earlier row exactly. The columns you choose decide what counts as a duplicate. Student ID is the field that should be unique, so compare that column. Only the chosen columns are compared. Because Name and Suburb match, the first row is kept and the second is deleted, even though the Phone differs. SUM does not produce an error for duplicates. It simply counts them twice, so totals, counts and averages become inaccurate.

Common mistakes: Remove Blank Rows deletes empty rows, not repeated ones. The tool that deletes rows repeating the same values is Data > Remove Duplicates. Different students can have the same mark, so comparing on Mark would delete real rows. Compare on a column that identifies a record, such as Email.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 50–91) and word search (Modules 17–91).

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Learning
Duo
A student wants to delete rows where the same student ID appears twice. Which setting is correct?
Run Remove Duplicates comparing only the Student ID columnRun Remove Duplicates comparing every column, including Date and Score
Matches
Run Remove Duplicates on the only copy of the raw data
↓
Rows are deleted permanently from the original, so there is no raw data left to check or recover. Make a copy of the sheet first.
Applying
Meanings
Term
Remove Duplicates
Meaning
A spreadsheet tool that deletes rows repeating the same values in the columns you choose to compare, keeping the first match. Always keep a copy of the raw data first.
Practice
SELECT DISTINCT house, yearLevel
Testing
Gaps
Data > Data Tools >
Check Answer
Spots
2Select A1:D50 on Clean
3Data > Remove Blank Rows

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Quick Questions

1. A student wants to delete rows where the same student ID appears twice. Which setting is correct?
A. Run Remove Duplicates comparing only the Student ID column ✓
B. Run Remove Duplicates comparing every column, including Date and Score
The columns you choose decide what counts as a duplicate. Student ID is the field that should be unique, so compare that column.
2. Before using Remove Duplicates on the original dataset, what should you do first?
A. Run it straight away because Undo is always available later
B. Save a copy of the raw data on a separate sheet or file ✓
Keep a copy of the raw data first. Once the file is saved and closed, the deleted rows cannot be recovered, and you may need the original to check your work.
3. Which statement describes what Remove Duplicates does?
A. It deletes later rows that repeat the same values in the chosen columns ✓
B. It highlights repeated rows but leaves every row in the data
Remove Duplicates permanently deletes rows. Highlighting repeated values is done with conditional formatting, which is a different tool.
4. Two rows have the same Name and Suburb, but different Phone numbers. You compare only Name and Suburb. What happens?
A. Both rows are kept because the Phone numbers differ
B. The second row is removed as a duplicate ✓
Only the chosen columns are compared. Because Name and Suburb match, the first row is kept and the second is deleted, even though the Phone differs.
5. Two rows match in every column. Which row does Remove Duplicates keep?
A. The first row that appears in the list ✓
B. The last row that appears in the list
The tool keeps the first match it finds and deletes the later repeats.

Match the Pairs

Data > Remove Duplicates → Opens the tool that deletes rows repeating the same values in the columns you tick, keeping the first match
Tick only the StudentID column → Rows are treated as duplicates when their StudentID matches, even if other columns differ
Before removing duplicates, keep a copy of the raw data so deleted rows can be recovered → Right-click sheet tab > Move or Copy > Create a copy
To count a row as a duplicate only when every column matches, select all the columns to compare → Select All in the Remove Duplicates box
Run Remove Duplicates on the only copy of the raw data → Rows are deleted permanently from the original, so there is no raw data left to check or recover. Make a copy of the sheet first.
Tick only the Gender column to remove duplicate students → Many different students share the same gender, so rows would be wrongly deleted. Compare a column that identifies the record, such as StudentID.

Key Term

Remove Duplicates
A spreadsheet tool that deletes rows repeating the same values in the columns you choose to compare, keeping the first match. Always keep a copy of the raw data first.

Fill in the Blanks

1. Data > Data Tools > Remove Duplicates
Hint: Type the name of the spreadsheet tool that deletes repeated rows.
2. 1. Copy the raw data sheet before cleaning
Hint: Type the action you do to make a backup of the raw data before removing rows.
3. Tick all columns to match whole rows
Hint: Type the word for how many columns to tick when two rows must be identical in every field.
4. Remove Duplicates keeps the first match
Hint: Type the word that says which of the matching rows the tool keeps.
5. Row 2: Ava,7 Row 5: Ava,7 Remove Duplicates deletes row 5
Hint: Type the row number of the repeated row that gets deleted.

Spot the Error

Question 1
A Copy sheet Raw to Clean
B Select A1:D50 on Clean
C Data > Remove Blank Rows
D Tick column: StudentID
Line C — Remove Blank Rows deletes empty rows, not repeated ones. The tool that deletes rows repeating the same values is Data > Remove Duplicates.
Question 2
A Copy sheet Raw to Clean
B Select A1:C20 on Clean
C Data > Remove Duplicates
D Tick column: Mark
Line D — Different students can have the same mark, so comparing on Mark would delete real rows. Compare on a column that identifies a record, such as Email.
Question 3
A Sheet Raw holds the original
B Work on a copy named Clean
C Run Remove Duplicates on Raw
Line C — The tool permanently deletes rows. Run it on the Clean copy so the Raw data stays safe.
Question 4
A Edit Raw directly, no copy
B Select the data range
C Data > Remove Duplicates
Line A — Always keep a copy of the raw data first. Without a copy, deleted rows cannot be recovered or checked later.
Question 5
A Select only the header row A1
B Data > Remove Duplicates
C Tick column: StudentID
Line A — Select the whole table, A1:D50, so every row can be compared. Selecting only the header row leaves no data rows to check.

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