Understanding Group by Rollup with Examples in Snowflake

Data analysis stands as the backbone of informed decision-making for modern businesses. Snowflake, renowned for its robust functionalities, offers a comprehensive suite of features for advanced data manipulation. Among these, the 'Group by Rollup' function emerges as a cornerstone for in-depth analysis. In this guide, we delve into the intricacies of Group by Rollup in Snowflake, exploring its features and real-world applications.

What is Group by Rollup in Snowflake?

Group by Rollup is a powerful feature within Snowflake that facilitates data aggregation across multiple levels in a single query. It extends the capabilities of traditional SQL queries, allowing users to generate subtotal rows alongside grand totals, offering a holistic view of the data.

The Essence of Group by Rollup

This functionality enables analysts to create summarized results across various dimensions without the need for multiple queries. By specifying columns for grouping, Group by Rollup produces aggregated results at different levels, providing insights into hierarchically organized data.

How Does Group by Rollup Work?

The syntax for Group by Rollup in Snowflake involves specifying columns for grouping within the query. 

 

Example Dataset:

Let's consider a hypothetical dataset containing sales information with columns: Region, Product Category, and Sales Amount.

Region	Product Category	Sales Amount
North	Electronics	$500
South	Fashion	$700
East	Electronics	$300
North	Fashion	$600
South	Electronics	$400
East	Fashion	$550

SQL Query Using Group by Rollup:

sqlCopy code

SELECT
    Region,
    Product_Category,
    SUM(Sales_Amount) AS Total_Sales
FROM
    Sales_Data
GROUP BY ROLLUP (Region, Product_Category);

Resultant Output:

Region	Product Category	Total Sales
North	Electronics	$500
North	Fashion	$600
North	NULL	$1,100
South	Electronics	$400
South	Fashion	$700
South	NULL	$1,100
East	Electronics	$300
East	Fashion	$550
East	NULL	$850
NULL	Electronics	$1,200
NULL	Fashion	$1,850
NULL	NULL	$3,050

This output showcases the aggregated sales figures obtained using Group by Rollup in Snowflake. It provides totals for each region, product category, and overall grand totals. The NULL rows represent subtotal rows at different hierarchical levels, aiding in comprehensive data analysis across multiple dimensions.