oneselfone

转载于 2018-11-05 23:41:00 发布 · 58 阅读

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CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/csslcww/p/9912371.html

本文详细介绍了使用MyBatis进行多表关联查询的方法，包括one2many和many2one类型的关联查询，通过具体的XML配置示例，展示了如何在不同场景下实现多表查询，适用于希望提高数据库操作效率的开发者。

1.one2many-多表连接查询


<mapper namespace="com.abc.dao.INewsLabelDao">
    
    <!-- 多表连接查询 -->

    <resultMap type="NewsLabel" id="newslabelMap">
        <id column="ptid" property="id"/>
        <result column="ptname" property="name"/>
        <collection property="children" ofType="NewsLabel">
            <id column="cdid" property="id"/>
            <result column="cdname" property="name"/>
        </collection>
    </resultMap>

    <select id="selectNewsLabelById" resultMap="newslabelMap">
        select pt.id ptid,pt.name ptname,cd.id cdid,cd.name cdname
        from newslabel pt,newslabel cd
        where pt.id=cd.pid and pt.id=#{xxx}
    </select>

</mapper>

2.one2many-多表单独查询

<mapper namespace="com.abc.dao.INewsLabelDao">
    
    <!-- 多表单独查询 -->

    <select id="selectChildrenByParent" resultMap="newslabelMap">
        select id,name from newslabel where pid=#{jjj}
    </select>

    <resultMap type="NewsLabel" id="newslabelMap">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <collection property="children" 
                    ofType="NewsLabel"
                    select="selectChildrenByParent"
                    column="id"/>
    </resultMap>

    <select id="selectNewsLabelById" resultMap="newslabelMap">
        select id,name from newslabel where id=#{xxx}
    </select>

</mapper>

3.one2many-多表单独查询2

<mapper namespace="com.abc.dao.INewsLabelDao">
    
    <!-- 多表单独查询 -->

    <select id="selectChildrenByParent" resultMap="newslabelMap">
        select id,name from newslabel where pid=#{jjj}
    </select>

    <resultMap type="NewsLabel" id="newslabelMap">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <collection property="children" 
                    ofType="NewsLabel"
                    select="selectChildrenByParent"
                    column="id"/>
    </resultMap>

</mapper>

4.many2one-多表单独查询

<mapper namespace="com.abc.dao.INewsLabelDao">
    
    <!-- 多表单独查询 -->

    <resultMap type="NewsLabel" id="newslabelMap">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <association property="parent" 
                     javaType="NewsLabel"
                     select="selectNewsLabelById"
                     column="pid"/>
    </resultMap>
    
    <select id="selectNewsLabelById" resultMap="newslabelMap">
        select id,name,pid from newslabel where id=#{jjj}
    </select>

</mapper>

转载于:https://www.cnblogs.com/csslcww/p/9912371.html