Cursor Expressions

Nested dataset, evaluates to a cursor.

Example:

DECLARE
    CURSOR cur_dept_info IS
        SELECT dept_id,
            CURSOR(SELECT emp_id  -- cursor expression
                       FROM employee
                       WHERE emp_dept_id = dept_id) emp_info
            FROM departments;
    l_dept_id departments.dept_id%TYPE;
    rc_emp_info SYS_REFCURSOR;  -- weakly-typed refcursor provided by Oracle
    l_emp_id employee.emp_id%TYPE;
BEGIN
    OPEN cur_dept_info;
    LOOP
        FETCH cur_dept_info INTO l_dept_id, rc_emp_info;
        EXIT WHEN cur_dept_info%NOTFOUND;
        LOOP
            FETCH rc_emp_info INTO l_emp_id;
            EXIT WHEN rc_emp_info%NOTFOUND;
            dbms_output.PUT_LINE('l_emp_id: ' || l_emp_id);
        END LOOP;
    END LOOP;
    CLOSE cur_dept_info;
END;