OJ_server/src/main/resources/mapper/ContestRegistrationMapper.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="space.anyi.serve.mapper.ContestRegistrationMapper">

    <insert id="upsert">
        INSERT INTO dev.contest_registration (contest_id, user_id)
        VALUES (#{contestId}, #{userId})
        ON CONFLICT (contest_id, user_id) DO UPDATE SET delete_flag = 0
    </insert>

    <select id="selectByContestId" resultType="space.anyi.serve.entity.contest.ContestRegistrationVo">
        SELECT r.id, r.user_id AS userId, u.username, r.created_at AS createdAt
        FROM dev.contest_registration r
        JOIN dev.user u ON u.id = r.user_id AND u.delete_flag = 0
        WHERE r.contest_id = #{contestId} AND r.delete_flag = 0
        ORDER BY r.created_at
    </select>

</mapper>