To categorize a set of values using the GROUP BY command in SQL, you would typically use the following syntax:

SELECT column_name, aggregate_function(column_name)
FROM table_name
GROUP BY column_name;

In this syntax, column_name is the name of the column you want to group the values by, and table_name is the name of the table you are querying. The aggregate_function is a function that performs a calculation on a set of values in the specified column, such as SUM, COUNT, or AVG.

Here’s an example of how you could use the GROUP BY command to categorize a set of sales data by region:

SELECT region, SUM(sales_amount) AS total_sales
FROM sales_data
GROUP BY region;

In this example, region is the column we want to group by, and sales_data is the name of the table we are querying. We are using the SUM function to calculate the total sales amount for each region.