oracle中的substr比较给力,以字符串abcde为例

select substr('abcde',1,3) as str from dual
结果abc

select substr('abcde',3,5) as str from dual
结果cde

select substr('abcde',3,50) as str from dual
不报错,结果cde

从1开始，到几就是第几位，简单易用