（外键）mybatis的sqlmapper配置文件中处理外键提供两种解决方案

现在有两张表professional专业表和classes班级表，专业表中的proid作为班级表的外键存在。

professional：

public class Professional {
private int proid;
private String proname;
private String prodesc;
private Date createdate;

classes：

public class Classes {
private int clsid;
private String clsname;
private String clsdesc;
private Professional pro;
private Date createdate;
private Date enddate;

第一种解决方案：

<resultMap type="Classes" id="ClsResult">
<id column="clsid"  property="clsid"/>
<result column="clsname"  property="clsname"/>
<result column="clsdesc"  property="clsdesc"/>
<result column="createdate" property="createdate"/>
<result column="enddate" property="enddate"/>
<association column="proid" property="pro" javaType="Professional" select="com.oa.dao.professionalDao.selProById"></association>
</resultMap>
<select id="selClsById" parameterType="int" resultMap="ClsResult">
SELECT * FROM classes WHERE clsid = #{id}
</select>

第二种解决方案（表连接查询）：

如果采用表连接的方式进行查询，那么resultmap中每一个列名column和属性property都必须要指定

<resultMap type="Classes" id="ClsResult">
<id column="clsid"  property="clsid"/>
<result column="clsname"  property="clsname"/>
<result column="clsdesc"  property="clsdesc"/>
<result column="createdate" property="createdate"/>
<result column="enddate" property="enddate"/>

<association property="pro" javaType="Professional">
<result column="proid" property="proid"/>
<result column="proname" property="proname"/>
<result column="prodesc" property="prodesc"/>
<result column="pcreatedate" property="createdate"/>
</association>
</resultMap>

<select id="selClsById" parameterType="int" resultMap="ClsResult">
select classes.*,professional.proname,professional.prodesc,professional.createdate as pcreatedate from classes INNER JOIN professional on classes.proid = professional.proid where classes.clsid = 1
</select>