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SQL DENSE_RANK
SQL DENSE_RANK
Learn how to assign rankings to rows without gaps in the sequence
Understanding DENSE_RANK
DENSE_RANK is a window function that assigns a rank to each row within a result set, similar to RANK. The key difference is that DENSE_RANK assigns consecutive ranks without gaps when handling ties. This makes it perfect for scenarios where you want a compact ranking sequence while still properly handling ties.
Basic Syntax
Common DENSE_RANK Interview Questions
- How does DENSE_RANK differ from RANK in handling ties?
- When would you choose DENSE_RANK over other ranking functions?
- How can you find videos in the top 3 view tiers for each user?
- How would you identify users in different engagement level tiers?
Common DENSE_RANK Patterns
1. Tiered Rankings
Create consecutive tiers or levels based on metrics.
2. Performance Categories
Categorize items into performance levels without gaps.
3. Multi-Dimensional Rankings
Rank based on multiple criteria with consistent numbering.
Advanced DENSE_RANK Examples
Example 1: User Engagement Tiers
Analyze user engagement across different metrics:
Example 2: Monthly Performance Tiers
Track video performance tiers over time:
Best Practices for DENSE_RANK
1. Understanding Dense Ranking
Know how DENSE_RANK works:
- Assigns same rank to tied values
- Next rank is consecutive (no gaps)
- Perfect for tiered classifications
2. Choosing the Right Function
Select DENSE_RANK when you need:
- Consecutive rankings without gaps
- Proper handling of ties
- Compact tier or level assignments
3. Performance Optimization
Optimize your DENSE_RANK queries:
- Index columns used in ORDER BY and PARTITION BY
- Filter data before applying DENSE_RANK
- Consider materialized views for frequent rankings
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