Problem
Oracle frequently mixes SQL into the design round. Write a query to find duplicate records in a table and explain JOIN types and ACID.
Requirements
- Find rows duplicated on (name, email)
- Explain INNER vs LEFT vs FULL JOIN
- Explain ACID and normalization
What evaluators look for
- Correct GROUP BY ... HAVING COUNT(*) > 1
- Clear understanding of indexing impact
- Trade-offs of normalization vs denormalization
Extension
Now delete duplicates keeping the lowest id — write that query.