转换为Codeigniter查询构建器

Question

我有一个查询，在codeigniter框架中没有运气。

 SELECT l_student_meta.value
 FROM l_student_meta 
 LEFT JOIN m_student ON m_student.id = l_student_meta.student_id
 WHERE l_student_meta.tag = "name" 
 AND m_student.id = 844;