Characteristics of Rollup
- SQL’s ROLLUP function streamlines multi-level data analysis using a single query.
- As an extension of GROUP BY, ROLLUP enables aggregations across various dimensions and hierarchical levels within a single SQL query.
- Results obtained with SQL ROLLUP are unsorted; an ORDER BY clause is necessary to arrange the data in a desired order.
Rollup in SQL Server
The ROLLUP operator enhances the capabilities of the GROUP BY clause by enabling the computation of subtotals and grand totals for a set of columns. It produces a result set that incorporates rows at various levels of aggregation. ROLLUP streamlines the aggregation process by eliminating the need for separate queries to obtain subtotals and totals, resulting in a more streamlined and efficient approach. It is a powerful extension of the GROUP BY clause, enabling users to generate summary reports effortlessly.
Syntax:
SELECT column, aggregate_function(column)
FROM table
GROUP BY ROLLUP (column);
In this syntax:
- ‘column’ represents the column by which you wish to group your data.
- ‘aggregate_function(column)’ is an optional step, allowing you to specify an aggregation function (e.g., SUM, COUNT, AVG) for performing calculations on the grouped data.
- ‘table’ designates the table being queried.
- ‘GROUP BY’ is a clause used to specify a single column or multiple columns to create a group on which the aggregate operation is performed.
- ‘ROLLUP’ is used with the combination of the GROUP BY clause for creating multiple groups (i.e., grouping set) and hierarchically applies the aggregate function.