**Course Title:** SQLite Mastery: Lightweight Database Management **Section Title:** Aggregate Functions and Grouping Data **Topic:** Filtering grouped data using HAVING ### Introduction Welcome to this topic on filtering grouped data using HAVING. In the previous topic, we explored how to group data using GROUP BY. However, when working with grouped data, we often need to filter the results based on certain conditions. This is where the HAVING clause comes in. ### What is the HAVING Clause? The HAVING clause is used in conjunction with the GROUP BY clause to filter grouped data. It is used to specify conditions that must be met by each group in order for the group to be included in the results. ### Syntax The basic syntax of the HAVING clause is as follows: ```sql SELECT column1, column2 FROM tablename GROUP BY column1, column2 HAVING condition; ``` ### Examples Let's consider the following table, which we will use as an example: ```markdown +---------+----------+--------+ | Company | Division | Sales | +---------+----------+--------+ | ABC Inc | North | 10000 | | ABC Inc | North | 20000 | | ABC Inc | South | 30000 | | DEF Inc | North | 15000 | | DEF Inc | North | 25000 | | DEF Inc | South | 35000 | +---------+----------+--------+ ``` In this example, we want to find the companies that have total sales greater than 50000 per division. We can use the HAVING clause to achieve this: ```sql SELECT Company, Division, SUM(Sales) AS TotalSales FROM sales GROUP BY Company, Division HAVING SUM(Sales) > 50000; ``` This will return the following result: ```markdown +----------+----------+-----------+ | Company | Division | TotalSales| +----------+----------+-----------+ | ABC Inc | South | 30000 | | DEF Inc | South | 35000 | +----------+----------+-----------+ ``` ### Best Practices When using the HAVING clause, keep the following best practices in mind: * Use the HAVING clause in conjunction with the GROUP BY clause. * Use aggregate functions such as SUM, COUNT, and AVG in the HAVING clause. * Use comparison operators such as =, <, >, <=, >=, and <> in the HAVING clause. ### Common Use Cases The HAVING clause is commonly used in the following scenarios: * Filtering grouped data based on aggregate values. * Finding groups that meet certain conditions. * Grouping and filtering data based on multiple conditions. ### Example Use Case Suppose we have an online store and we want to find the products that have an average price greater than 50 and a total sales quantity greater than 100. We can use the HAVING clause to achieve this: ```sql SELECT ProductName, AVG(Price) AS AveragePrice, SUM(Quantity) AS TotalQuantity FROM sales GROUP BY ProductName HAVING AVG(Price) > 50 AND SUM(Quantity) > 100; ``` This will return the products that meet the specified conditions. ### Conclusion In this topic, we explored the HAVING clause and how it is used to filter grouped data. We learned the syntax, examples, and best practices of using the HAVING clause. We also discussed common use cases and provided an example use case. **What's Next?** In the next topic, we will learn about advanced data aggregation techniques. **Leave a Comment/Ask for Help** If you have any questions or need help with the concepts covered in this topic, feel free to leave a comment below. **External Resources:** For more information on the HAVING clause, you can refer to the SQLite documentation: [https://www.sqlite.org/lang_select.html](https://www.sqlite.org/lang_select.html).