MLS-C01 Exploratory Data Analysis Practice Question
A data scientist is performing EDA on a dataset with 1 million rows. They suspect the dataset contains duplicate rows. Which approach is most efficient to identify duplicates in Amazon SageMaker Studio?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use DuckDB SQL query: SELECT COUNT(*) - COUNT(DISTINCT *) FROM table.
DuckDB is an in-process SQL OLAP database that can run on a single machine and efficiently handle large datasets. Option A (Python loop) is slow; Option B (pandas drop_duplicates) may be memory-intensive; Option D (Athena) is serverless but incurs cost and latency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Write a Python script that loops through each row and compares to a set of seen rows.
Why it's wrong here
Looping is inefficient for 1M rows.
- ✗
Use pandas drop_duplicates and then check the length difference.
Why it's wrong here
pandas may run out of memory for large datasets.
- ✓
Use DuckDB SQL query: SELECT COUNT(*) - COUNT(DISTINCT *) FROM table.
Why this is correct
DuckDB efficiently processes large DataFrames in-memory.
- ✗
Use Amazon Athena to query the S3 data with COUNT(DISTINCT *).
Why it's wrong here
Athena charges per query and has overhead.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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