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Finding and Removing Duplicates
Last Updated: April 13, 2026
Ashish Pratap Singh
11 min read
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Sample Data
The Pattern
Approach 1: GROUP BY + HAVING (Detection)
Approach 2: Self-Join (Identification)
Approach 3: ROW_NUMBER (Deduplication via SELECT)...
Approach 4: DELETE with CTE + ROW_NUMBER
Edge Cases
When to Use Each Approach
Common Mistakes
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Nth Highest / Nth Va...
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Consecutive Records ...
