SELECT * FROM student;

--Example 1
SELECT student_id, first_name, last_name, fees_required,
LAG(fees_required) OVER (ORDER BY fees_required ASC) AS prev_fees_required
FROM student
ORDER BY student_id ASC;

--Example 2
SELECT student_id, first_name, last_name, fees_required,
LAG(fees_required) OVER (ORDER BY fees_required ASC) AS prev_fees_required
FROM student
ORDER BY fees_required ASC;

--Example 3
SELECT student_id, first_name, last_name, fees_required,
LAG(fees_required, 3, 0) OVER (ORDER BY fees_required ASC) AS prev_fees_required
FROM student
ORDER BY fees_required ASC;

http://www.databasestar.com/oracle-lag/

A few examples of the LAG function.

Oracle LAG Function

sql, Oracle

SQL