select ename,sal,comm,sal+comm from emp;

select ename,sal,comm,sal+comm from emp where comm is not null
union
select ename,sal,comm,sal+0 from emp where comm is null;

select ename,sal,comm,sal+nvl(comm,0) from emp;

select ename,sal,comm,sal+nvl(comm,-500) from emp;
select ename,sal,comm,sal+coalesce(comm,0) from emp;
select * from sz;
insert into sz values(null,'banán');
select N from sz;
select NVL(N,'AKÁRKI') from sz;
select NVL(N,'AKÁRKI'),gy from sz;
select user from dual;

SELECT UID FROM DUAL;
select * from emp;
select empno,ename,mgr from emp;

select level szint,empno,ename,mgr from emp
connect by mgr = prior empno
start with job='PRESIDENT';

select level szint,empno,ename,mgr from emp
connect by prior mgr = empno
start with ename='ADAMS';

select level szint,empno,ename,mgr from emp
connect by prior mgr = empno
start with ename='FORD';

select level szint,empno,ename,mgr from emp
connect by mgr = prior empno
start with ename='JONES';

select level szint,empno,ename,mgr from emp
connect by mgr = prior empno
start with job='MANAGER';
Adjuk meg az ORAUSER.VAGYONOK tábla alapján KAIN unokáinak az össz-vagyonát.

SELECT nev ---sum(vagyon)-- lpad(' ',4*(level-1))|| nev,vagyon
FROM orauser.vagyonok
where level=3
START WITH  nev='KAIN'
CONNECT BY  PRIOR nev = apja;

-------------------------------------------------------------------------

select * from sz where rownum<=5;
select * from sz where rownum=5;
select * from sz where rownum<=5;
select rownum from sz where rownum<=5;
select rownum,* from sz where rownum<=5;
select rownum from sz where rownum<=5;
select * from sz where rownum<=5;
select rownum,sz.* from sz where rownum<=5;
select rownum,sz.* from sz where rownum=5;

select * from sz where rownum<=5
minus
select * from sz where rownum<=4;

select * from (select rownum sz.* from sz where rownum<=5) where rownum=5;


select * from (select rownum x,sz.* from sz where rownum<=5) where x=5;

select n from sz order by 1
union
select ename from emp order by 1;

select n from sz 
union
select ename from emp order by 1;

select * from (select n from sz order by 1) where rownum=1
union
select * from (select ename from emp order by 1) where rownum=1;