> For the complete documentation index, see [llms.txt](https://dev117uday.gitbook.io/databases/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev117uday.gitbook.io/databases/sql/summarization.md).

# Summarization

* When we are aggregating data, we generally remove the detail data that lies below the summarize table.
* The whole point of aggregation is to replace detail data with summaries. This is where subtotals comes in!
* A grouping set is a set of columns by which you group.
* The PostgreSQL `ROLLUP` is a subclass of the GROUP BY clause that offers shorthand for defining '**multiple grouping sets**'