How to use group by in mysql

GROUP BY in MySQL can group data by specified columns and apply aggregate functions (such as SUM, COUNT, AVG) to summarize the data within the group, which can be used to analyze large data sets. Specific steps include specifying the columns to group by, selecting the aggregate function to calculate, and applying the aggregation.

Usage of GROUP BY in MySQL

GROUP BY Overview

## The #GROUP BY keyword is used to group data based on specified columns and calculate aggregate functions (such as SUM, COUNT, AVG, etc.) for each group. This enables us to summarize and analyze data from large datasets.

Syntax

<code>SELECT 聚合函数(列名)
FROM 表名
GROUP BY 分组列</code>

Steps to use GROUP BY

1. Specify the columns to group by:Use the GROUP BY clause to specify the columns by which to group data.
2. Select an aggregate function to calculate: Use aggregate functions (such as SUM, COUNT, AVG, etc.) to summarize data within groups.
3. Apply aggregation: The aggregation function will be applied to each grouping and return a summary value.

Example

<code>SELECT SUM(销售额)
FROM 销售表
GROUP BY 产品类别</code>

This query will group the sales in the sales table based on product category and return the total sales per product category.

Extra Tip

GROUP BY eliminates duplicate values, meaning each group contains only unique values.
• You can specify multiple grouping columns, separated by commas.
• You can use the HAVING clause to filter the grouped results.
• GROUP BY can be used with ORDER BY to sort by group.

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