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Top 50 data cleaning Interview Questions

The most frequently asked data cleaning questions across all roles and companies, ranked by real interview frequency. Updated daily.

50questions
~16htotal time
683companies covered
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1
SQL & Data ManipulationStart here. 33 questions · ~630 min
SQL Duplicate Record CleanupMedium
Practice
Recently asked

Identify duplicate transaction rows, retain the earliest record, and delete later duplicates safely.

deduplicationdata cleaningtransactionsOracleDiscoverMicrosoft
Deduplicate Streaming RecordsHard
Practice
Recently asked

Deduplicate events within a 24-hour lateness window while retaining the earliest ingested record for each event.

Window FunctionsLag/Leaddata cleaningGoogle
Extract KPIs from Unstructured LogsMedium
Practice

Parse release log text and calculate event counts, error rates, average latency, and p95 latency per software release.

data parsingdata cleaningAggregationsApple
Find Duplicate Records in SQLMedium
Practice

Identify duplicate rows by key columns and return each duplicated group with its count.

data cleaningGroup Bydata anomalyMicrosoft
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2
Coding10 questions · ~191 min
Clean or Transform Data in PythonMedium
Practice

Normalize Phenom Talent Marketplace skill labels, apply aliases, deduplicate them, and rank by frequency using hashing and sorting.

data cleaningpythonPhenomClearManpower
Parse and Clean Nested JSONHard
Practice

Recursively extract and normalize nested TetraScience assay measurements while preserving inherited experiment and sample context.

data cleaningjson parsingProgrammingTetraScienceBridgestone Americas
Transform Nested JSON at ScaleHard
Practice
Recently asked

Flatten, clean, deduplicate, and aggregate nested JSON events in one linear pass.

deduplicationaggregationdata cleaningAdobe
Parse and Normalize TransactionsHard
Practice

Parse messy Plaid transaction records, normalize fields, and deduplicate valid transactions in one pass.

data cleaningdata processingStringsPlaid
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3
Behavioral & Leadership7 questions · ~134 min
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