Mybatis 随记

1 一对多collection

1.1 嵌套查询

一次关联hz+mx信息，Mybatis会自动合并相同的HZ信息

        <!-- 查询 部门 + 部门员工 -->
	<select id="getDeptById" resultMap="MyDept" >
		SELECT
			d.id did,
			d.dept_name dept_name,
			e.id,
			e.last_name last_name,
			e.email email,
			e.gender gender
		FROM
			tbl_dept d
		LEFT JOIN tbl_employee e ON d.id = e.d_id
		WHERE
			d.id = #{id}
	</select>

	<resultMap type="com.Department" id="MyDept">
		<id column="did" property="id"/>
		<result column="dept_name" property="departmentName"/>
		
                <!--collection 也可以指定自己的resultMap-->
                <!--emps 对应com.Department 类中的属性名--> 
		<collection property="emps" ofType="com.Employee">
			<id column="eid" property="id"/>
			<result column="last_name" property="lastName"/>
			<result column="email" property="email"/>
			<result column="gender" property="gender"/>
		</collection>
	</resultMap>

 

1.2 子查询实现

https://blog.csdn.net/aodeng110/article/details/82850221