Using GROUP BY
You can find and use the GROUP BY function using an SQL query in the SQL View. It’s one of the simplest and most direct ways to access and control your data.
Breaking Down the Query
Consider, for example, an order data table consisting of the attributes below: Substitute the actual name of the table, the category or column heading, and the actual entry value that you’re looking for.
OrderID: A numeric value uniquely identifying each order. This field is the primary key for the database. Salesperson: A text value providing the name of the salesperson who sold the products. This field is a foreign key to another table containing personnel information. CustomerID: A numeric value corresponding to a customer account number. This field is also a foreign key, referencing a table containing customer account information. Revenue: A numeric value corresponding to the dollar amount of the sale.
When it comes time to conduct performance reviews for salespeople, the Orders table contains valuable information that may be used for that review. When evaluating Jim, you could, for example, write a simple query that retrieves all of Jim’s sales records: This would retrieve all records from the database corresponding to sales made by Jim: You could review this information and perform some manual calculations to develop performance statistics, but this would be a tedious task that you would have to repeat for each salesperson in the company. Instead, you can replace this work with a single GROUP BY query that calculates each salesperson’s statistics in the company. You write the query and specify that the database should group the results based upon the Salesperson field. You may then use any of the SQL aggregate functions to perform calculations on the results. Here’s an example. If you executed the following SQL statement: You would get the following results: As you can see, this powerful function allows you to generate brief reports from within a SQL query, providing valuable business intelligence to the manager conducting the performance reviews. The GROUP BY clause is often used in databases for this purpose and is a valuable tool in the DBA’s bag of tricks.
