How to Calculate Percentiles in Snowflake

When performing data analysis, understanding the distribution of your data is crucial. One of the most useful ways to do this is by calculating percentiles. In this tutorial, we will walk you through the process of calculating percentiles in Snowflake using its built-in SQL functions.

What are Percentiles?

Percentiles are values that divide a dataset into 100 equal parts, giving you insights into how the data is distributed. For example, the 90th percentile represents the value below which 90% of the data points fall.

Calculating Percentiles in Snowflake

Snowflake provides a range of powerful window functions that you can use to calculate percentiles. One of the most common functions for this task is the PERCENTILE_CONT function, which calculates a specific percentile over a sorted set of data.

Syntax of PERCENTILE_CONT

SELECT PERCENTILE_CONT(0.9) WITHIN GROUP (ORDER BY column_name) AS percentile_90
FROM your_table;

In this example, we calculate the 90th percentile of a column named column_name from the table your_table. The PERCENTILE_CONT function interpolates between values if the requested percentile falls between two data points.

Example Query

SELECT PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY sales_amount) AS median_sales
FROM sales_data;

In this query, we are calculating the median sales amount (50th percentile) from the sales_data table.

Understanding the Results

After executing the query, Snowflake returns the value at the specified percentile. This allows you to understand the data distribution and make informed decisions based on statistical analysis.

Advanced Percentile Calculations

You can also calculate multiple percentiles in one query by using PERCENTILE_CONT for various percentile values:

SELECT
    PERCENTILE_CONT(0.25) WITHIN GROUP (ORDER BY sales_amount) AS percentile_25,
    PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY sales_amount) AS median_sales,
    PERCENTILE_CONT(0.75) WITHIN GROUP (ORDER BY sales_amount) AS percentile_75
FROM sales_data;

Conclusion

Calculating percentiles in Snowflake is simple and effective using the PERCENTILE_CONT function. By leveraging this function, you can gain valuable insights into your data, which can drive better decision-making and analysis.