mysql-返回不同记录的条件最小最大值

我有一个数据库转储 the geonames website for Great Britain . 它包含大约60000条记录。 示例数据如下:

id       |     name    |   admin1   |   admin2   |  admin3  |  feature_class  |  feature_code
-------------------------------------------------------------------------------------------
2652355  |   Cornwall  |   ENG      |     C6     |          |      A          |    ADM2
11609029 |   Cornwall  |   ENG      |            |          |      L          |    RGN
6269131  |   England   |   ENG      |            |          |      A          |    ADM1

功能代码为ADM2的第一条记录表示它是管理级别2 具有特征码RGN的分段记录意味着它是一个区域。

我想按地名搜索记录以建立自动完成功能。 如果记录具有相同的名称,如果其中一个记录是一个区域,即具有特征代码RGN,那么我只想返回 否则,我想返回与具有最低id的名称匹配的记录。

我试过以下方法,但不起作用:

   SELECT IF(t0.feature_code = 'RGN', MAX(t0.id), MIN(t0.id)) as id
       , CONCAT_WS(', ', t0.name,
                  IF(t3.name != t0.name, t3.name, NULL),
                  IF(t2.name != t0.name, t2.name, NULL),
                  IF(t1.name != t0.name, t1.name, NULL)) AS name
     FROM locations t0
  LEFT JOIN locations t1 ON t1.admin1 = t0.admin1 AND t1.feature_code = 'ADM1'
  LEFT JOIN locations t2 ON t2.admin2 = t0.admin2 AND t2.feature_code = 'ADM2'
  LEFT JOIN locations t3 ON t3.admin3 = t0.admin3 AND t3.feature_code = 'ADM3'
  WHERE 
      (t0.feature_class IN ('P', 'A') OR (t0.feature_class = 'L' AND t0.feature_code = 'RGN' ) )
      AND t0.name like 'Cornwall%' 
  GROUP BY CONCAT_WS(', ', t0.name,
                     IF(t3.name != t0.name, t3.name, NULL),
                     IF(t2.name != t0.name, t2.name, NULL),
                     IF(t1.name != t0.name, t1.name, NULL))
  ORDER BY t0.name 

它返回错误的记录:

id      | name
---------------------------
2652355 | Cornwall, England