What does group by mean in sql

The GROUP BY clause divides the data set into groups based on the specified column or expression, grouping records with the same grouping by value. It can be used for summary calculations or aggregation of data, such as calculating total, average, and maximum sales for each product type.

The meaning of GROUP BY clause in SQL

The GROUP BY clause is a powerful tool in SQL Tool for grouping records in a dataset for summary calculations or aggregation.

How it works:

The GROUP BY clause groups the records in the data set based on the specified column or expression. When grouping, records with the same Group By value are grouped together.

Syntax:

<code>SELECT 列名, 聚合函数(列名)
FROM 表名
WHERE 条件
GROUP BY 分组依据</code>

Example:

The following query groups the sales data in the table "Sales" by product type , and summarize the total sales of each type of product:

<code>SELECT ProductType, SUM(SalesAmount)
FROM Sales
GROUP BY ProductType</code>

Effect:

This query will return a result set in which each row represents a product type, and Total sales of this type of product.

Other uses:

The GROUP BY clause can also be used to perform the following operations:

• Calculate the average, maximum, and minimum aggregate functions such as values.
• Count duplicates.
• Delete duplicate rows.

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