Mybatis-----查询结果合并成集合

Posted 2022-07-18 mb62caa7d6f2477

如上查询结果，通过主表左连接出来多条记录。

目前的查询结果共有12条记录，但是根据 id来看，实际上只有2条主表记录，其它的都是

通过主表左连接出来的。

如何让查询结果只有2条?

MyBatis提供了合并的语法

@Data
public class Subsystem 
    private int subsystemId;
    private String subsystemKey;
    private String subsystemName;
    private Integer sn;
    private boolean selected;
    //持有Page对象集合
    private List<Page> pages;


@Data
public class Page 
    private int pageId;
    private String pageKey;
    private String pageName;
    private boolean selected;
    private Integer parentPageId;
    private Integer sn;
    private List<Page> subPages;

<select id="list" resultMap="listWithPage">
         SELECT
             ts.id,
             ts.subsystem_key,
             ts.subsystem_name,
             tp.id as page_id,
             tp.page_key,
             tp.page_name,
             ts.SN,
             tp.SN as page_sn,
             tp.parent_page_id
         FROM t_subsystem ts
         LEFT JOIN t_page tp ON ts.id = tp.subsystem_id
         ORDER BY ts.SN , tp.SN
    </select>

    <resultMap id="listWithPage"  
               <!-- 这里返回最终的对象类型-->
               type="$package.Subsystem">
        <id property="subsystemId" column="id"/>
        <result property="subsystemName" column="subsystem_name"/>
        <result property="subsystemKey" column="subsystem_key"/>
        <result property="sn" column="sn"/>
        <collection property="pages" 
                       <!-- 这里填写持有的集合对象类型-->
                     ofType="$package.Page">
            <id property="pageId" column="page_id"/>
            <result property="pageKey" column="page_key"/>
            <result property="pageName" column="page_name"/>
            <result property="sn" column="page_sn"/>
            <result property="parentPageId" column="parent_page_id"/>
        </collection>
    </resultMap>