在进行查询操作时，应尽量避免频繁使用格式转换以实现ORACLE+SQL性能优化的全面提升

在查询时尽量少用格式转换 如用 WHERE a.order_no = b.order_no 不用 WHERE TO_NUMBER (substr(a.order_no, instr(b.order_no, '.') - 1) = TO_NUMBER (substr(a.order_no, instr(b.order_no, '.') - 1)