spring-boot-realworld-example-app/src/main/resources/mapper/CommentReadService.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="io.spring.infrastructure.mybatis.readservice.CommentReadService">
    <sql id="selectCommentData">
        SELECT
        C.id commentId,
        C.body commentBody,
        C.created_at commentCreatedAt,
        <include refid="io.spring.infrastructure.mybatis.readservice.ArticleReadService.profileColumns"/>
        from comments C
        left join users U
        on C.user_id = U.id
    </sql>

    <select id="findById" resultMap="commentData">
        <include refid="selectCommentData"/>
        where C.id = #{id}
    </select>
    <select id="findByArticleId" resultMap="commentData">
        <include refid="selectCommentData"/>
        where C.article_id = #{articleId}
    </select>

    <resultMap id="commentData" type="io.spring.application.data.CommentData">
        <id column="commentId" property="id"/>
        <result column="commentBody" property="body"/>
        <result column="commentCreatedAt" property="createdAt"/>
        <result column="commentCreatedAt" property="updatedAt"/>
        <association property="profileData" resultMap="io.spring.infrastructure.mybatis.readservice.ArticleReadService.profileData"/>
    </resultMap>
</mapper>