Oracle (+) connector usage, oracle connector usage

Oracle (+) connector usage, oracle connector usage

In the Oracle PL-SQL, left and right connections can also be implemented as follows

Example:

SELECT stu_name, class_nameFORM students, classesWHERE students. classid (+) = classes. id

The preceding SQL query uses the right connection.
That is, the other side of the "(+)" is the connection direction.
All records on the right side of the equal sign are displayed, regardless of whether they are matched on the left,
In other words, no matter whether a department does not have an employee in the previous example,
The Department name is displayed in the query results.