How does this CASE part of the solution code work for the "answering business questions with SQL" guided project?

Solution Code:

%%sql

WITH country_or_other AS
    (
     SELECT
       CASE
           WHEN (
                 SELECT count(*)
                 FROM customer
                 where country = c.country
                ) = 1 THEN "Other"
           ELSE c.country
       END AS country,
       c.customer_id,
       il.*
     FROM invoice_line il
     INNER JOIN invoice i ON i.invoice_id = il.invoice_id
     INNER JOIN customer c ON c.customer_id = i.customer_id
    )

Can someone explain how this specific part of the code written below behaves. Does it act like a GROUP BY in this case? I’m confused how this condition works to group countries with count = 1 as “Other”

where country = c.country

@davidaguilaratx

Case is used to create categories in a particular column. In this case, the Case statement creates categories in the table country. It does so using this:

 WHEN (
                 SELECT count(*)
                 FROM customer
                 where country = c.country
                ) = 1 THEN "Other"

When the customer in a country is 1, it categorizes it as Other, otherwise it keeps it as the original name of the country.

I like to refer you to this.