1. When is an outer join used instead of a natural join? 2. Explain the processing order of a correlated sub query. 3. Explain the following statement regarding SQL: Any query that can be written...

1. When is an outer join used instead of a natural join?

2. Explain the processing order of a correlated sub query.

3. Explain the following statement regarding SQL: Any query that can be written using the sub query approach can also be written using the joining approach but not vice versa.