What mistakes do candidates make on this question?

Just restates the definition — any candidate who read the docs can say this No practical example showing WHEN you'd choose one over the other Missing the connection to real business problems (top-N per group, pagination) No discussion of performance implications with large datasets Doesn't mention NTILE or other window functions that complete the picture

mediumSQLAnswer Breakdown

DENSE_RANK vs RANK — Why Your Window Function Answer Isn't Good Enough

Knowing the gap difference isn't enough for FAANG interviews. See the answer that covers edge cases, performance, and real-world usage patterns.

Original Interview Question

Demonstrate the difference between DENSE_RANK() and RANK()

View Full Question

✗

The Weak Answer (What Most Candidates Say)

RANK() assigns the same rank to ties but skips subsequent ranks. For example: 1, 2, 2, 4. DENSE_RANK() assigns the same rank to ties but doesn't skip ranks. For example: 1, 2, 2, 3. ROW_NUMBER() assigns unique sequential numbers regardless of ties: 1, 2, 3, 4.

⚠

Why This Answer Fails

1.Just restates the definition — any candidate who read the docs can say this
2.No practical example showing WHEN you'd choose one over the other
3.Missing the connection to real business problems (top-N per group, pagination)
4.No discussion of performance implications with large datasets
5.Doesn't mention NTILE or other window functions that complete the picture

✓

The FAANG-Level Answer

All three assign ranks, but the business context determines which to use:

sql
SELECT
  name, department, salary,
  RANK()       OVER (ORDER BY salary DESC) as rank_val,
  DENSE_RANK() OVER (ORDER BY salary DESC) as dense_val,
  ROW_NUMBER() OVER (ORDER BY salary DESC) as row_val
FROM employees;

name	salary	RANK	DENSE_RANK	ROW_NUMBER
Alice	120K	1	1	1
Bob	120K	1	1	2
Carol	100K	3	2	3

When to use each:

DENSE_RANK: "Top 3 salary levels" — when you want exactly 3 distinct values regardless of ties. E.g., Find the 3rd highest salary.
RANK: "Top 3 positions" with competition rules — like sports rankings where ties push others down
ROW_NUMBER: Pagination, deduplication (keep one row per group), or when you need guaranteed unique ordering

Real-world patterns I use constantly:

sql
-- Deduplication: keep latest record per user
WITH ranked AS (
  SELECT *, ROW_NUMBER() OVER (
    PARTITION BY user_id ORDER BY updated_at DESC
  ) AS rn
  FROM events
)
SELECT * FROM ranked WHERE rn = 1;

-- Top 3 products per category (no gaps)
WITH ranked AS (
  SELECT *, DENSE_RANK() OVER (
    PARTITION BY category ORDER BY revenue DESC
  ) AS dr
  FROM products
)
SELECT * FROM ranked WHERE dr <= 3;

Performance note: All three are computed in the same sort pass. The window ORDER BY determines the sort cost — adding PARTITION BY converts it to a partial sort (much cheaper on large tables).

Key Takeaway

The definition is table stakes. The interview-winning answer shows WHICH function solves WHICH business problem, with real query patterns (deduplication, top-N per group) that you've used in production.

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DENSE_RANK vs RANK — Why Your Window Function Answer Isn't Good Enough

Knowing the gap difference isn't enough for FAANG interviews. See the answer that covers edge cases, performance, and real-world usage patterns.

Original Interview Question

Demonstrate the difference between DENSE_RANK() and RANK()

View Full Question

✗

The Weak Answer (What Most Candidates Say)

⚠

Why This Answer Fails

1.Just restates the definition — any candidate who read the docs can say this
2.No practical example showing WHEN you'd choose one over the other
3.Missing the connection to real business problems (top-N per group, pagination)
4.No discussion of performance implications with large datasets
5.Doesn't mention NTILE or other window functions that complete the picture

✓

The FAANG-Level Answer

All three assign ranks, but the business context determines which to use:

sql
SELECT
  name, department, salary,
  RANK()       OVER (ORDER BY salary DESC) as rank_val,
  DENSE_RANK() OVER (ORDER BY salary DESC) as dense_val,
  ROW_NUMBER() OVER (ORDER BY salary DESC) as row_val
FROM employees;

name	salary	RANK	DENSE_RANK	ROW_NUMBER
Alice	120K	1	1	1
Bob	120K	1	1	2
Carol	100K	3	2	3

When to use each:

DENSE_RANK: "Top 3 salary levels" — when you want exactly 3 distinct values regardless of ties. E.g., Find the 3rd highest salary.
RANK: "Top 3 positions" with competition rules — like sports rankings where ties push others down
ROW_NUMBER: Pagination, deduplication (keep one row per group), or when you need guaranteed unique ordering

Real-world patterns I use constantly:

sql
-- Deduplication: keep latest record per user
WITH ranked AS (
  SELECT *, ROW_NUMBER() OVER (
    PARTITION BY user_id ORDER BY updated_at DESC
  ) AS rn
  FROM events
)
SELECT * FROM ranked WHERE rn = 1;

-- Top 3 products per category (no gaps)
WITH ranked AS (
  SELECT *, DENSE_RANK() OVER (
    PARTITION BY category ORDER BY revenue DESC
  ) AS dr
  FROM products
)
SELECT * FROM ranked WHERE dr <= 3;

Key Takeaway

Want to know if YOUR answer is weak or strong?

Paste your answer and get instant AI-powered feedback with a FAANG-level improved version.

Analyze My Answer — Free

3 free analyses per day. No sign-up required.

DENSE_RANK vs RANK — Why Your Window Function Answer Isn't Good Enough

The Weak Answer (What Most Candidates Say)

Why This Answer Fails

The FAANG-Level Answer

When to use each:

Real-world patterns I use constantly:

Want to know if YOUR answer is weak or strong?

Related Interview Questions

DENSE_RANK vs RANK — Why Your Window Function Answer Isn't Good Enough

The Weak Answer (What Most Candidates Say)

Why This Answer Fails

The FAANG-Level Answer

When to use each:

Real-world patterns I use constantly:

Want to know if YOUR answer is weak or strong?

Related Interview Questions