That's all we wanted to show you in this part! Before we review, let's do a quick summary.

We've talked about three methods to compare different business groups in a single query.

1. In Method 1, we use a CASE WHEN construction in a CTE to label business objects. In the outer query, we group the rows by these labels. Groups are shown in separate rows.

   WITH name_of_cte AS (
     SELECT
       ...,
       CASE
         WHEN ...
         ELSE ...
       END AS group_label
     FROM table_name
   )
   SELECT
     group_label,
     COUNT(...) 
   FROM name_of_cte
   GROUP BY group_label;
   

2. In Method 2, we use multiple COUNT/SUM(CASE WHEN...) statements to create groups. The groups are shown in separate columns. We can also add more groups.

   SELECT
     group_column,
     COUNT(CASE
       WHEN ... THEN ...
     END) AS group_one,
     COUNT(CASE
       WHEN ... THEN ...
     END) AS group_two
   FROM table_name
   GROUP BY group_column;
   

3. In Method 3, each group is calculated in a separate CTE. Groups are then combined in the outer query.

   WITH group_one AS (...), 
   group_two AS (...)
   SELECT
     group_one.column_name,
     group_two.column_name
   FROM group_one
   FULL OUTER JOIN group_two
     ON ...;
   

How about a short quiz?