<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.casic.missiles.mapper.customer.CustomerSampleMapper"> <select id="selectMaxSampleNo" resultType="Long"> SELECT IFNULL(MAX(RIGHT(sample_no, 12)), 0) FROM customer_sample_info </select> </mapper>