08-one2many

Posted 2021-01-17 csslcww

    <!-- 多表连接查询 -->

<?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="com.abc.dao.ICountryDao">

    <!-- 多表连接查询 -->

    <!-- 定义结果映射关系 -->
    <resultMap type="Country" id="countryMap">
        <id column="cid" property="cid"/>
        <result column="cname" property="cname"/>
        <!-- ofType解释为element of type ，元素类型 -->
        <collection property="ministers" ofType="Minister">
            <id column="mid" property="mid"/>
            <result column="mname" property="mname"/>
        </collection>
    </resultMap>

    <select id="selectCountryById" resultMap="countryMap">
        select cid,cname,mid,mname
        from country,minister
        where cid=countryId and cid=#{xxx}
    </select>

</mapper>

 多表单独查询、

<mapper namespace="com.abc.dao.ICountryDao">

    <!-- 多表单独查询 -->
    
    <select id="selectMinisterByCountry" resultType="Minister">
        select mid,mname from minister where countryId=#{ooo}
    </select>

    <!-- 定义结果映射关系 -->
    <resultMap type="Country" id="countryMap">
        <id column="cid" property="cid"/>
        <result column="cname" property="cname"/>
        <!-- ofType解释为element of type ，元素类型 -->
        <collection property="ministers" 
                    ofType="Minister"
                    select="selectMinisterByCountry"
                    column="cid"/>
    </resultMap>

    <select id="selectCountryById" resultMap="countryMap">
        select cid,cname from country where cid=#{xxx}
    </select>

</mapper>