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  • many2many

    多表连接查询

    <mapper namespace="com.abc.dao.IStudentDao">
    
        <!-- 多表连接查询 -->
    
        <resultMap type="Student" id="studentMap">
            <id column="sid" property="sid" />
            <result column="sname" property="sname" />
            <collection property="courses" ofType="Course">
                <id column="cid" property="cid" />
                <result column="cname" property="cname" />
            </collection>
        </resultMap>
    
        <select id="selectStudentById" resultMap="studentMap">
            select sid,sname,cid,cname
            from student,course,middle
            where sid=studentId and cid=courseId and sid=#{xxx}
        </select>
    
    </mapper>


    多表单独查询

    <mapper namespace="com.abc.dao.IStudentDao">
    
        <!-- 多表单独查询 -->
    
        <select id="selectCourseById" resultType="Course">
            select cid,cname from course where cid=#{jjj}
        </select>
    
        <resultMap type="Middle" id="middleMap">
            <id column="id" property="id"/>
            <association property="course" 
                         javaType="Course"
                         select="selectCourseById"
                         column="courseId"/>
        </resultMap>
    
        <select id="selectMiddleByStudent" resultMap="middleMap">
            select id,courseId from middle where studentId=#{ooo}
        </select>
    
        <resultMap type="Student" id="studentMap">
            <id column="sid" property="sid" />
            <result column="sname" property="sname" />
            <collection property="courses" 
                        ofType="Course"
                        select="selectMiddleByStudent"
                        column="sid"/>
        </resultMap>
    
        <select id="selectStudentById" resultMap="studentMap">
            select sid,sname from student where sid=#{xxx}
        </select>
    
    </mapper>

    多表复杂查询

    <mapper namespace="com.abc.dao.IStudentDao">
    
        <!-- 多表复杂查询 -->
    
        <select id="selectCourseById" resultType="Course">
            select cid,cname from course where cid=#{ooo}
        </select>
    
        <resultMap type="Student" id="studentMap">
            <id column="sid" property="sid" />
            <result column="sname" property="sname" />
            <collection property="courses" 
                        ofType="Course"
                        select="selectCourseById"
                        column="courseId"/>
        </resultMap>
    
        <select id="selectStudentById" resultMap="studentMap">
            select sid,sname,courseId
            from student,middle
            where sid=studentId and sid=#{xxx}
        </select>
    
    </mapper>

     

     

     

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  • 原文地址:https://www.cnblogs.com/csslcww/p/9912383.html
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