You did well! All right, it's time to wrap things up. First, let's summarize what we've covered in this part:

1. A CASE WHEN statement checks for one or more conditions and returns a value when it finds the first matching condition. If there is no ELSE clause and no matching conditions, CASE WHEN returns NULL.

   CASE
     WHEN condition_1 THEN result_1
     WHEN condition_2 THEN result_2
     ...
     ELSE result
   END
   

2. To add a new column, and thus a custom classification of business products, you can use CASE WHEN in the SELECT clause:

   SELECT 
     CASE
       WHEN ... THEN ...
     END AS sample_column
   FROM table;
   

3. You can use CASE WHEN in a GROUP BY clause to create your own grouping. The same CASE WHEN clause must also appear in the SELECT clause:

   SELECT 
     CASE
       WHEN ... THEN ...
     END AS sample_column,
     COUNT(*) AS sample_count
   FROM table
     ...
   GROUP BY
     CASE WHEN ... THEN ...
     END;
   

4. You can create a custom count of business objects using CASE WHEN inside a COUNT() or SUM() function:

   SELECT 
     COUNT(CASE
       WHEN ... THEN column_name
     END) AS count_column
   FROM table;
   

   SELECT 
     SUM(CASE
       WHEN ... THEN 1
     END) AS count_column
   FROM table;
   

How about a short quiz now?