The meaning of group by in sql

In SQL, the GROUP BY clause is used to group and calculate aggregate values ​​based on specified columns: Group data: Organize data into groups based on specific columns. Calculate aggregate values: Perform summary calculations, such as sums, averages, or counts, on column values ​​for each group.

Meaning of GROUP BY

In SQL, GROUP BY clause is used Groups data based on specified columns and calculates aggregate values ​​for each group. Aggregated values ​​are obtained by applying a specific operation (such as sum, average, or count) to the values ​​of all rows in the group.

How to use GROUP BY

The GROUP BY clause is used in the SELECT statement, and its syntax format is as follows:

SELECT 聚合函数(列名)
FROM 表名
GROUP BY 列名1, 列名2, ...

Among them:

• Aggregation function is the operation to be performed on the values ​​within the group, such as SUM(), AVG (), or COUNT().
• Column name is the column used to group the data.

Example

Consider the following table:

##王五English75赵六English85##To calculate the average score for each category, you can use For the following query:

Name	Category	Achievements
张三	MATHEMATICS	80
李四	MATHEMATICS	90

SELECT 类别, AVG(成绩)
FROM 表名
GROUP BY 类别;

the result will be:

Category##Mathematics85English80

Average Grade

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