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 NameOfCTE AS (
     SELECT
       ...,
       CASE
         WHEN ...
         ELSE ...
       END AS GroupLabel
     FROM TableName
   )
   SELECT
     GroupLabel,
     COUNT(...) 
   FROM NameOfCTE
   GROUP BY GroupLabel;
   

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
     GroupColumn,
     COUNT(CASE
       WHEN ... THEN ...
     END) AS GroupOne,
     COUNT(CASE
       WHEN ... THEN ...
     END) AS GroupTwo
   FROM TableName
   GROUP BY GroupColumn;
   

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

   WITH GroupOne AS (...), 
   GroupTwo AS (...)
   SELECT
     GroupOne.ColumnName,
     GroupTwo.ColumnName
   FROM GroupOne
   FULL OUTER JOIN GroupTwo
     ON ...;
   

How about a short quiz?