[질의튜닝]order by desc가 인덱스 타게 하려면

csql> create table member_tbl(id int primary key, name varchar(10));
csql> insert into member_tbl values (1, 'marry'), (2, 'john'), (3,'billy'), (4, 'willy');
csql> ;x
csql> ;plan simple
csql> select * from member_tbl order by id for orderby_num() between 1 and 2;
Query plan:
 Index scan(member_tbl member_tbl, pk_member_tbl_id, member_tbl.id range (-2147483648 ge_inf max))
           id  name
===================================
            1  'marry'
            2  'john'

csql> select * from member_tbl order by id desc for orderby_num() between 1 and 2;
Query plan:
 Sort(order by)
    Sequential scan(member_tbl member_tbl)
           id  name
===================================
            4  'willy'
            3  'billy'

csql> create unique index idx_u_member_tbl_id on member_tbl(id desc);

csql> select * from member_tbl order by id desc for orderby_num() between 1 and 2;
Query plan:
 Index scan(member_tbl member_tbl, idx_u_member_tbl_id, member_tbl.id range (-2147483648 ge_inf max))
           id  name
===================================
            4  'willy'
            3  'billy'