与列匹配后需要获取给定字符串中的最大值

设置:

create table t (c varchar2(10));
insert into t values ('123');
insert into t values ('456');
insert into t values ('789');
commit;

查询:

select c, instr('123456789',c) as pos
  from t
 order by 2 desc 
 fetch first 1 row only;

结果:

C                 POS
---------- ----------
789                 7