![]() For example, if you want to retrieve the total number of products and group them by id, you can run the following query: SELECT id, SUM(product_quantity) Using the WITH ROLLUP modifier with GROUP BY allows including to the summary output extra rows that indicate higher-level (super-aggregate) summary processes. GROUP BY orders.city GROUP BY and the WITH ROLLUP modifier Then you can run the query below: SELECT orders.city, COUNT(*) So, let’s imagine that you want to get rows with the same values from the Employees and Orders tables on the basis of matching values between them. There are three types of JOINS in MySQL, but in this section, we’ll review INNER JOIN. MySQL GROUP BY can be combined with JOIN in order to group rows with the same values from one or several tables, based on a related column between them. HAVING SUM(total_cost) < 500 GROUP BY with JOIN The statement below returns ids and the total cost that is less than 500: SELECT id, total_cost The HAVING clause is used instead of WHERE with aggregate functions. ![]() You can add HAVING to the GROUP BY syntax to find rows with particular conditions. Using the above syntax, we’ll know the number of products for each city. Here is an example of MySQL GROUP BY with the COUNT aggregation function: SELECT city, COUNT(product_quantity)
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