Display distinct cities in ADDRESSES(id, street_name, number, city, state)?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of SQL & Databases conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
To retrieve a list of unique cities without duplicates from the ADDRESSES table, use the DISTINCT keyword:
SELECT DISTINCT city
FROM addresses
ORDER BY city ASC;
### Performance Consideration:
The DISTINCT clause forces the database engine to perform a deduplication sort or hash aggregation over the candidate rows. On tables containing millions of records, ensure an index exists on the city column (CREATE INDEX idx_addresses_city ON addresses(city)) to enable an index skip-scan or fast stream deduplication.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.