electromagnetic-data-new/electrmangnetic/src/main/resources/sqlmapper/EdFileInfoMapper.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.electromagnetic.industry.software.manage.mapper.EdFileInfoMapper">

    <select id="maxPrjId" resultType="java.lang.String">
        select max(id)
        from ed_file_info
        where prj_dir = true
    </select>
</mapper>