title: left join table with two conditions
body: <p>I need to <code>left join</code> between two tables to take courses in the first table, and non-existent in the second table. But I also want to take courses that mark smaller than 60 in the second table(Even if it was exist in two tables).</p>
  
  <pre><code>SELECT   offerd_course.id,offerd_course.course_id,
           offerd_course.instructor_name,offerd_course.hour, 
           offerd_course.course_name, 
           offerd_course.day,offerd_course.place,
           offerd_course.type
  FROM offerd_course
  LEFT JOIN student_course
  ON offerd_course.course_id = student_course.course_id 
  WHERE  student_course.mark &gt;=60 AND student_course.course_id IS NULL 
  </code></pre>
  
  <p>How can do it ?</p>