I'm curious about the theory of ORACLE INDEX.

create table emp3(
  no number,
  name varchar2(10),
  salary number
 );

 insert into emp3 values (1, 'Seo Geonchang', 200);
 insert into emp3 values (2, 'Ko Jongwook', 100);
 insert into emp3 values (3, 'Lee Taek-geun', 150);
 insert into emp3 values (4, 'Danidon', 150);
 insert into emp3 values (5, 'Kim Min-sung', 200);
 insert into emp3 values (6, 'Chataein', 250);
 insert into emp3 values (7, 'Kim Ha-sung', 150);
 insert into emp3 values (8, 'Park Dong-won', 200);
 insert into emp3 values (9, 'Lim Byung-wook', 100);

--  Create index 
 create index idx_name
 on emp3(name);

 -- Name output without index
 select name from emp3;

 -- Index post-use name
 select name from emp3
 where name > '0';

 -- Name output without index -- sort occurred. More processing speed on a large number of data
 select min(name) from emp3; -- Output value: Jongwook Ko

-- Index x
select max(name) from emp3; -- Output value: Chae Tae-in

-- Index o, hint
select /*+ index_desc(emp3 idx_name)*/ name
from emp3
where name > '0'
and growum = 1;-- Output value: Seo Geon-chang
-- This method can produce incorrect output results if there is a change in the index column.

-- It can be processed by the first_row max method.
select /*+ index_desc(emp3 idx_name)*/ max(name)
from emp3
where name > '0';-- Output value: Chae Tae-in