Suppose there are many columns based on column X. I will be using GROUP BY on only two columns, even though there are 10 more columns. Is it a choice to use all columns for GROUP BY?

In SQL, GROUP BY is used to aggregate rows that share the same values in the specified columns. You are not required to include every column in the GROUP BY clause. In fact, including unnecessary columns can lead to a larger number of groups, which may degrade performance and produce less meaningful results. The typical rule is: include only the columns that define the logical grouping you care about. For example, if you want to calculate the total sales per region and per product category, you would GROUP BY region, category. The remaining columns can be aggregated using functions like SUM, AVG, COUNT, etc. If you include all columns, each distinct combination becomes a separate group, often resulting in a row per original record, which defeats the purpose of aggregation. Therefore, it is both a choice and a best practice to use only the columns that are relevant to the aggregation logic.