lemonBeans/ruoyi-system/src/main/resources/mapper/system/EmplsMapper.xml

<?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.ruoyi.system.mapper.EmplsMapper">

    <select id="getByEmpl" resultType="java.lang.Long">
        select emtlId from EMPLS where emplId = #{userName}
    </select>
</mapper>