title: Passing multiple columns in myBatis <assoctiation>
body: <p>I want to know, how do we pass multiple columns in a myBatis association tag.</p>
  
  <p>For example, I have the following xml snippet in one my mapper.xml file:</p>
  
  <pre><code>&lt;resultMap type="com.mysite.domain.CourseBuilderCourses" id="ResultMapWithAssmnts" extends="BaseResultMap"&gt;
  
      &lt;association property="totalAssignmentCnt" column="course_id" select="selectTotalAssgnmentsCnt"/&gt;
      &lt;association property="totalAssessmentCnt" column="course_id" select="selectTotalAssesmentsCnt"/&gt;  
  &lt;!--  see this association &gt;&gt; --&gt; &lt;association property="subscription" column="course_id" select="com.mysite.persistence.mybatis.CourseSubscriptionMapper.selectByUsercId"/&gt; 
  
    &lt;/resultMap&gt;
  </code></pre>
  
  <p>As you can see, the <code>&lt;association&gt;</code> with <code>property</code> subscription has only one column, <code>course_id</code></p>
  
  <p>I want to pass 2 columns to it, and therefore the resultant code, how do we do that?</p>
  
  <p>I tried the following combinations, none worked:</p>
  
  <pre><code>column="{course_id,user_id}"   // null,null are passed as parameters 
  column="course_id,user_id"   // null,null are passed as parameters 
  column="{COURSE_ID=course_id,USER_ID=user_id}"   // null,null are passed as parameters 
  </code></pre>
  
  <p>but if I pass single, 
      column="{course_id}" or column="course_id"</p>
  
  <p>works without any issues.</p>
  
  <p>Any idea guys?</p>