Diagnosing problems using anti-join

Another powerful join in SQL is the anti-join. It is particularly useful in identifying which records are causing an incorrect number of records to appear in join queries.
You will also see another example of a subquery here, as you saw in the first exercise on semi-joins. Your goal is to identify the currencies used in Oceanian countries!
Example
.....Note that not all countries in Oceania were listed in the resulting inner join with currencies. Use an anti-join to determine which countries were not included!