Introduction
Custom classifications of business objects
Custom grouping of business objects
Custom counting of business objects
Instruction
Excellent! The same kind of report can also be created using SUM() instead of COUNT(). Take a look:
SELECT
SUM(CASE
WHEN ship_country = 'USA' OR ship_country = 'Canada' THEN 1
END) AS free_shipping,
SUM(CASE
WHEN ship_country != 'USA' AND ship_country != 'Canada' THEN 1
END) AS paid_shipping
FROM orders;
In the above query, we used SUM() with CASE WHEN instead of COUNT(). The CASE WHEN construction inside the SUM() function is very similar to that inside COUNT(), but you can see that we pass a 1 to SUM() when the condition is satisfied. This is a bit different from COUNT(), where we passed in the column name.
Despite their minor differences, both SUM() and COUNT() produce identical results in this query.
Exercise
The template presents a solution to the previous exercise. Modify it so that it uses SUM() instead of COUNT().
Stuck? Here's a hint!
You need to change the function and the CASE WHEN instruction inside it.
