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Handle nulls, duplicates, and inconsistent timestamp formats in data.

SQLmedium0.3 min readPremium
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Apple
Key Concepts Tested
partition
Expert AnswerPremium
55 wordsInterview-ready
**Nulls**: COALESCE(col, default); IS NULL checks; avoid NULL in NOT IN. **Duplicates**: ROW_NUMBER() OVER (PARTITION BY key ORDER BY ts DESC) keep rn=1; or GROUP BY with aggregations. **Timestamps**: Parse to ISO 8601; TRY_CAST or regex; store UTC. **Pipeline**: Validation layer → quarantine failures → log for remediation....
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