树形结构维护，关系保存，没查到关系判空

cdssman-service/src/main/resources/mapper/KlRelationMapper.xml

@@ -141,14 +141,14 @@
         <if test="relationId!=null">
             AND relation_id = #{relationId}
         </if>
-        ) k,
+        ) k LEFT JOIN
         kl_relation r
-        WHERE
+        ON
         k.endId = r.start_id
         AND k.relationId = r.relation_id
-        ) m,
+        ) m LEFT JOIN
         kl_concept kc
-        WHERE
+        ON
         m.medId = kc.id
     </select>
     <select id="findDisNameAll" resultType="com.diagbot.dto.GetAllForRelationDTO">