Differentiate between join and outer join?
Outer joins return all rows from at least one of the tables or views mentioned within the FROM clause, as long as those rows get together any WHERE or HAVING search conditions.
All rows are retrieved from the left table referenced along with a left outer join, and all rows from the right table referenced in a right outer join. All rows from both tables are returned within a full outer join.
A table can be joined to itself within a self-join.