Discover how SQL window functions can enhance your data analysis. This guide provides a brief overview and examples to help you get started quickly.
Examples of SQL Window Functions
ROW_NUMBER() Assigns a unique number to each row:
SELECT name, score, ROW_NUMBER() OVER (ORDER BY score DESC) as rank
FROM exam_scores;
RANK() Ranks rows, skipping ranks for ties:
SELECT name, score, RANK() OVER (ORDER BY score DESC) as rank
FROM exam_scores;
DENSE_RANK() Ranks rows without skipping ranks for ties:
SELECT name, score, DENSE_RANK() OVER (ORDER BY score DESC) as rank
FROM exam_scores;
PERCENT_RANK() Calculates the percentile rank of rows:
SELECT name, score, PERCENT_RANK() OVER (ORDER BY score DESC) as percentile_rank
FROM exam_scores;
NTILE() Divides rows into a specified number of groups:
SELECT name, score, NTILE(4) OVER (ORDER BY score DESC) as quartile
FROM exam_scores;
FAQ
What are SQL window functions?
They perform calculations over a set of rows defined by an OVER clause.
How do I use the ROW_NUMBER() function in SQL?
It assigns a unique number to each row within a window. Use it with the OVER clause.
What is the difference between the RANK() and DENSE_RANK() functions in SQL?
RANK() skips numbers after ties; DENSE_RANK() does not.
How does the PERCENT_RANK() function work in SQL?
It provides a rank between 0 and 1, representing the row's percentile position.
Conclusion
SQL window functions are invaluable for analyzing data. Start utilizing ROW_NUMBER(), RANK(), and NTILE() to uncover insights in your data. For more details, read this article on SQL window functions A Beginners Guide to SQL Window Functions.