sql新用法和字符串拼接

<?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.atguigu.spzx.manager.mapper.SysRoleMapper">

    <!--  映射查询到的字段 -->
    <resultMap id="sysRoleMap" type="com.atguigu.spzx.model.entity.system.SysRole" autoMapping="true"></resultMap>

    <!-- 用于select查询公用抽取的列 -->
    <sql id="columns">
        id
        ,role_name,role_code,description,create_time,update_time,is_deleted
    </sql>

    <select id="findByPage" resultMap="sysRoleMap">
        select
        <include refid="columns"/>
        from sys_role
        <where>
            <if test="roleName !=null and roleName != ''">
                and role_name like concat('%',#{roleName},'%')
            </if>
        </where>
        order by id desc
    </select>
</mapper>