优化查询未分合奏班的班级

mec-biz/src/main/resources/config/mybatis/ClassGroupMapper.xml

@@ -341,12 +341,8 @@
         </if>
     </select>
     <select id="findNoClassSubjects" resultMap="ClassGroup">
-        SELECT * FROM class_group cg
-        WHERE cg.id_ NOT IN
-        (SELECT cgr.sub_class_group_id_ FROM class_group_relation cgr
-        LEFT JOIN class_group cg ON cg.id_ = cgr.class_group_id_
-        WHERE cg.music_group_id_ = #{musicGroupId})
-        AND cg.music_group_id_ = #{musicGroupId} AND type_ = 'NORMAL' AND cg.del_flag_ = 0
+        SELECT cg.* FROM class_group cg LEFT JOIN class_group_relation cgr ON cgr.sub_class_group_id_=cg.id_
+        WHERE cg.music_group_id_=#{musicGroupId} AND cg.type_ = 'NORMAL' AND cg.del_flag_ = '0' AND cgr.sub_class_group_id_ IS NULL
     </select>
 
     <select id="countTeacherNum" resultType="java.lang.Integer">