用instr 直接取最右端的点的位置：
SQL> select substr('/upload/UserFiles/..ea85a945e72bc71fcffca399_140.jpg',instr('/upload/UserFiles/..ea85a945e72bc71fcffca399_140.jpg','.',-1,1)+1) from dual;
SUBSTR('/UPLOAD/USERFILES/..EA
------------------------------
jpg
SQL> select substr('/upload/UserFiles/..ea85a945e72bc71fcffca399_140.jpg',instr('/upload/UserFiles/..ea85a945e72bc71fcffca399_140.jpg','.',-1,1)+1) from dual;
SUBSTR('/UPLOAD/USERFILES/..EA
------------------------------
jpg
