How to use the group by statement in MySQL?

In MySQL, the GROUP BY statement is used to group the query results based on one or more columns. It is often used with aggregate functions (such as COUNT, SUM, AVG, etc.) to perform calculations on the grouped data.

The basic syntax of the GROUP BY statement is as follows:

Select column1, column2, … from table name grouped by column1, column2, …

In the GROUP BY clause, you can specify one or more columns to indicate how to group the data. Multiple columns should be separated by commas, with column 1, column 2, and so forth indicating the columns to group by.

Here is an example demonstrating how to use the GROUP BY statement to calculate the number of employees in each department:

Show the number of employees in each department.

In the above example, we group the “employees” table by the “department” column and use the COUNT(*) function to calculate the number of employees in each department. The final result will be grouped by department and display the number of employees in each department.

Note: When using the GROUP BY statement, if columns in the SELECT clause are not listed in the GROUP BY clause, they must be parameters of aggregate functions. Otherwise, an error will occur.