How do you find duplicate rows in a table?medium
Answer
Group by the duplicate-defining columns and filter groups with COUNT(*) greater than one.
Explanation
The key is defining what duplicate means. For full-row duplicates, group by all relevant columns. For business duplicates, group by natural keys like email or order id.
Hint: reason from constraints before calculating.
Follow-upHow would you keep only the latest row from each duplicate group?