Usage of Oracle (+) connectors

In Oracle Pl-sql, the left and right connections can also be implemented in the following way

Example:

SELECT Stu_name, class_nameform students, Classeswhere students.classid (+) = Classes.id

The above SQL query uses the right connection.
That is, the other side of the location where "(+)" is the direction of the connection.
Right connection description all records to the right of the equal sign are displayed, regardless of whether they are matched on the left side,
That is to say, in the above example, whether or not a department does not have an employee situation,
The name of this department will appear in the query results.

Usage of Oracle (+) connectors