12.2.4. GROUP BY – Aggregate Results

Try these first

1. 1.

   What does the GROUP BY clause do?

   Hint

   Think of how you can summarize data.

2. 2.

   Write a SQL query to count the number of users registered by email domain.

   Hint

   Look into substring functions for extracting data.

3. 3.

   What does the GROUP BY clause do in SQL?

   • It sorts the data in ascending order.
   • It combines rows that have the same value in specified columns.
   • It retrieves all records from a table.

   Hint

   Think about how we summarize information.

4. 4.

   True or False: GROUP BY can be used with aggregate functions like COUNT and AVG.

   • True
   • False

   Hint

   Recall our discussion on how to summarize data.

5. 5.

   Write a SQL query to find the total revenue generated per product category for the last year.

   Hint

   Make sure your date filters include the correct time frame.

6. 6.

   Create a report that shows how many times each user logged in within the last month, grouped by user.

   Hint

   Filter the relevant records before counting.