//返回值为doc
select substr('file.doc',instr('file.doc','.',-1)+1) from dual;
//返回值为cc
select substr('aaaa-bbbb-cc',instr('aaaa-bbbb-cc','-',-1)+1) from dual;
//返回值为doc
select substr('file.doc',instr('file.doc','.',-1)+1) from dual;
//返回值为cc
select substr('aaaa-bbbb-cc',instr('aaaa-bbbb-cc','-',-1)+1) from dual;