How to use rollup in sql

rollup is an aggregate function in SQL that is used to perform multi-level grouping and summary of data in a hierarchical structure. Its syntax is: rollup(expression). By aggregating data at different granularities, the rollup function can easily create multi-level aggregations, improve query performance, and allow users to explore data at different granularities.

Usage of rollup in SQL

What is rollup?

rollup is an aggregate function in SQL that is used to group and summarize data in a hierarchy. It allows users to perform multi-level aggregation of data, from the most detailed level to the most summary level.

How to use rollup?

The syntax of the rollup function is as follows:

<code class="sql">rollup(expression)</code>

Among them:

• expression: the expression to be grouped and aggregated, which can be a column name or an aggregate function or other calculations.

Usage example of rollup function:

Example 1: Summarize sales by "region" and "product" groups

<code class="sql">SELECT region, product, SUM(sales)
FROM sales_table
GROUP BY ROLLUP(region, product);</code>

This query will generate the following output:

<code class="sql">SELECT year, quarter, month, COUNT(order_id)
FROM orders_table
GROUP BY ROLLUP(year, quarter, month);</code>

Easily create multi-level aggregations.

• Improve query performance because aggregations are calculated in advance.

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