create table test_me  
(name varchar2(5),
 assignment_id varchar2(5),
 change_date varchar2(4),
 salary number);

insert into test_me values ('JOE', '16350', '2010', 103585); 

insert into test_me values ('JOE', '16350', '2012', 115000); 

insert into test_me values ('JOE', '16350', '2014', 135000); 

commit;

select * from test_me;

NAME  ASSIGNMENT_ID  CHANGE_DATE  SALARY
====  ============   ==========   =========
JOE   16350	     2010	  103585
JOE   16350          2012	  115000
JOE   16350          2014	  135000



Need help with creating SQL that will make Result should look like this:
                                                  (salary-previous)
NAME          salary        PREVIOUS_salary       INCREASE            CHANGE_DATE
=========     ==========    ===============       ================    ===========
JOE           135000         115000               20000               2014
JOE           115000         103585               11415               2012
JOE           103585         89000                14585               2010

--sample from link you sent
  SELECT c1 "Curr",
           LAG(c1) OVER (ORDER BY id) "Prev",
           c1 - LAG(c1) OVER (ORDER BY id) "Diff"
      FROM t1;
      Curr       Prev       Diff
---------- ---------- ----------
        40
        45         40          5
        35         45        -10
        37         35          2   <---- I don't want this record because I only want the ones > 2

ORA-00904: "DIFF": invalid identifier
00904. 00000 -  "%s: invalid identifier"
*Cause:    
*Action:
Error at Line: 117 Column: 7

--working sql
select first_name,  salary, previous_salary, Diff from
(
SELECT   
          first_name,  pro.proposed_salary_n Salary,
           LAG(pro.proposed_salary_n) OVER (ORDER BY pro.proposed_salary_n) Previous_salary,
           pro.proposed_salary_n - LAG(pro.proposed_salary_n) OVER (ORDER BY pro.proposed_salary_n) Diff,
           TO_CHAR(pro.change_date, 'RRRR') change_Date
        from PER_PAY_PROPOSALS PRO ,
              apps.per_all_Assignments_f paaf,
              apps.per_all_people_f papf
  where pro.assignment_id  in (7586) --(16350,7586,24270)
  and   pro.assignment_id = paaf.assignment_id
  and   papf.person_id = paaf.person_id
  and   TO_CHAR(pro.change_date, 'RRRR') > '2009'
    --and Diff > 8999          (This is line 117 column 7 in error)
  and sysdate between paaf.effective_start_date and paaf.effective_end_date
  and sysdate between papf.effective_start_date and papf.effective_end_date
  );

FIRST_NAME	SALARY	PREVIOUS_SALARY	DIFF
=========       ======= =============== ====
GEORGIANA	85878		
GEORGIANA	94423	85878	         8545 
GEORGIANA	109000	94423	        14577
GEORGIANA	132500	109000	        23500

--and Diff > 8999          (This is line 117 column 7 in error)

SELECT NAME, SALARY, PREVIOUS_SALARY,  nvl(salary-previous_salary,0) increase,CHANGE_DATE FROM (
select 'JOE' name ,sal salary , LAG(sal) OVER (ORDER BY empno) PREVious_salary,hiredate change_date from emp);

--increases greater than $8000
SELECT person_id, LAST_NAME , 
       SALARY, 
       PREVIOUS_SALARY,  
       nvl(salary-previous_salary,0) increase,
       CHANGE_DATE FROM (
select papf.last_name , papf.first_name, papf.person_id,
       pro.proposed_salary_n salary , 
       LAG(pro.proposed_salary_n) 
           OVER (PARTITION BY  PAPF.PERSON_ID ORDER BY pro.proposed_salary_N) AS PREVious_salary,
       pro.change_date  change_date 
           from PER_PAY_PROPOSALS PRO ,
                apps.per_all_Assignments_f paaf,
                apps.per_all_people_f papf
          where   pro.assignment_id = paaf.assignment_id
            and   papf.person_id = paaf.person_id
            AND   pro.change_date > '01-JAN-2009'
            and sysdate between paaf.effective_start_date and paaf.effective_end_date
            and sysdate between papf.effective_start_date and papf.effective_end_date 
            )
  WHERE   nvl(salary-previous_salary,0) >= 8000 
  order by 2,1,6 DESC;  
  
  
PERSON_ID   LAST_NAME	  SALARY    PREVIOUS_SALARY INCREASE     CHANGE_DATE
========    ============  ========  =============   ========     ===========
29033	      AARON	   26843	    17465        9378	    26-May-12
17702	      ABDOOL	   72558 	    60552       12006	    20-Feb-10
01649	      ABDULLAH	   54580.32	    45632     8948.32	    22-Nov-14
16947	      ABDUS-SABUUR 99007	    78946       20061	    30-Aug-14
04285	      ABREU	   54580.32	    45632     8948.32	    26-May-12
33203	      ACEVEDO      46378	    36126       10252	    12-Apr-14
12435	      ADAMES	   100000	    69608	30392	    22-Nov-14
16744	      ADAMES	   82337	    67337	15000	    24-Jul-10
00930	      ADAMS	   91433.52	    72558    18875.52        1-Mar-14