SQL ROWS BETWEEN

Understanding ROWS BETWEEN

ROWS BETWEEN is a window frame clause that defines a physical range of rows around the current row for window function calculations. Unlike RANGE BETWEEN which works with logical ranges of values, ROWS BETWEEN counts actual rows, making it perfect for sliding window calculations and running aggregates.

Basic Syntax

Common ROWS BETWEEN Interview Questions

What's the difference between ROWS BETWEEN and RANGE BETWEEN?
How can you calculate a 7-day moving average of video views?
How do you handle running totals with ROWS BETWEEN?
When would you choose ROWS over RANGE for window calculations?

Common ROWS BETWEEN Patterns

1. Running Totals

Calculate cumulative sums from the start of the partition to the current row.

2. Moving Averages

Calculate averages over a sliding window of rows.

3. Previous and Next Values

Compare current row with surrounding rows.

Advanced ROWS BETWEEN Examples

Example 1: Engagement Trends Analysis

Analyze user engagement patterns with moving windows:

Example 2: Content Performance Analysis

Compare video performance with historical context:

Best Practices for ROWS BETWEEN

1. Choose Window Size Carefully

Select an appropriate window size for your analysis:

Consider the nature of your data and business requirements
Larger windows smooth out fluctuations but may miss recent trends
Smaller windows are more sensitive to changes but may be noisy

2. Handle Edge Cases

Be mindful of how your window functions behave at the edges of your data:

First few rows may have incomplete windows for preceding calculations
Last few rows may have incomplete windows for following calculations
Consider using COALESCE or NULLIF to handle edge cases

3. Performance Considerations

Optimize your window function queries:

Index columns used in ORDER BY and PARTITION BY
Filter data before applying window functions
Consider materialized views for frequently used calculations

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