drop table external_emp

create table external_emp (
SEQ int,
EMPNO    NUMBER(4)    ,
ENAME             VARCHAR2(10) ,
JOB               VARCHAR2(9)  ,
MGR               NUMBER(4)    ,
HIREDATE          DATE         ,
SAL               NUMBER(7,2)  ,
COMM              NUMBER(7,2)  ,
DEPTNO            NUMBER(2)    
)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (1,7782,'CLARK','MANAGER',7839,to_date('09/JUN/81','DD/MON/RR'),2450,null,10)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (2,7839,'KING','PRESIDENT',null,to_date('17/NOV/81','DD/MON/RR'),5000,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (3,7934,'MILLER','CLERK',7782,to_date('23/JAN/82','DD/MON/RR'),1300,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (4,7369,'SMITH','CLERK',7902,to_date('17/DEC/80','DD/MON/RR'),800,null,20)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (5,7876,'ADAMS','CLERK',7788,to_date('12/JAN/83','DD/MON/RR'),1100,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (6,7902,'FORD','ANALYST',7566,to_date('03/DEC/81','DD/MON/RR'),3000,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7,7566,'JONES','MANAGER',7839,to_date('02/APR/81','DD/MON/RR'),2975,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (8,7788,'SCOTT','ANALYST',7566,to_date('09/DEC/82','DD/MON/RR'),3000,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (9,7499,'ALLEN','SALESMAN',7698,to_date('20/FEB/81','DD/MON/RR'),1600,300,30)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (10,7521,'WARD','SALESMAN',7698,to_date('22/FEB/81','DD/MON/RR'),1250,500,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (11,7654,'MARTIN','SALESMAN',7698,to_date('28/SEP/81','DD/MON/RR'),1250,1400,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (12,7698,'BLAKE','MANAGER',7839,to_date('01/MAY/81','DD/MON/RR'),2850,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (13,7844,'TURNER','SALESMAN',7698,to_date('08/SEP/81','DD/MON/RR'),1500,null,null)

insert into external_emp (SEQ,EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (14,7900,'JAMES','CLERK',7698,to_date('03/DEC/81','DD/MON/RR'),950,null,null)

commit

select empno, ename, job, hiredate, sal , deptno
from external_emp 
order by seq

select empno, ename, job, hiredate, sal , 
       nvl(deptno, lag(deptno) over (order by SEQ))  deptno
from external_emp 
order by seq

select empno, ename, job, hiredate, sal , 
       nvl(deptno, lag(deptno IGNORE NULLS) over (order by SEQ))  deptno
from external_emp 
order by seq