Mysql EXPLAIN表前面的空格，但随后它将作为文本出现 j4.owner_perception, j6.tl_perception, j2.tl_perception, j2.owner_perception +------+-----------

EXPLAIN表前面的空格，但随后它将作为文本出现

j4.owner_perception, 
j6.tl_perception, 

j2.tl_perception, 
j2.owner_perception 

+------+--------------+-------------+---------+-------------------+-------------+----------+--------------------+----------+----------------------------------------------+--+
|  id  | select_type  |   table     |  type   |  possible_keys    |    key      | key_len  |        ref         |  rows    |                    Extra                     |  |
+------+--------------+-------------+---------+-------------------+-------------+----------+--------------------+----------+----------------------------------------------+--+
|   1  | PRIMARY      | survey      | index   | NULL              | request_id  |     767  | NULL               |     476  | Using index; Using temporary; Using filesort |  |
|   1  | PRIMARY      | s           | eq_ref  | PRIMARY           | PRIMARY     |       4  | qo.survey.id       |       1  |                                              |  |
|   1  | PRIMARY      | <derived2>  | ref     | key0              | key0        |     153  | qo.s.request_id    |    1060  | Using where                                  |  |
|   1  | PRIMARY      | j4          | eq_ref  | PRIMARY           | PRIMARY     |       4  | j3.minumumownerid  |       1  | Using where                                  |  |
|   1  | PRIMARY      | <derived3>  | ref     | key0              | key0        |     153  | qo.s.request_id    |    2121  | Using where                                  |  |
|   1  | PRIMARY      | j6          | eq_ref  | PRIMARY           | PRIMARY     |       4  | j5.minumumtlid     |       1  | Using where                                  |  |
|   1  | PRIMARY      | <derived4>  | ref     | key0              | key0        |     153  | qo.s.request_id    |     530  | Using where                                  |  |
|   1  | PRIMARY      | j2          | eq_ref  | PRIMARY           | PRIMARY     |       4  | j1.maximumid       |       1  | Using where                                  |  |
|   4  | DERIVED      | history_gt  | range   | NULL              | request_id  |     152  | NULL               |  252406  | Using index for group-by                     |  |
|   3  | DERIVED      | history_gt  | index   | NULL              | request_id  |     152  | NULL               | 1009620  | Using where                                  |  |
|   2  | DERIVED      | history_gt  | index   | owner_perception  | request_id  |     152  | NULL               | 1009620  | Using where                                  |  |
+------+--------------+-------------+---------+-------------------+-------------+----------+--------------------+----------+----------------------------------------------+--+

SELECT 
      s.ticket_number, 
      s.request_id,
      j4.owner_perception, 
      j6.tl_perception,
      j2.tl_perception, 
      j2.owner_perception 
    FROM 
      survey s
         left join
         (SELECT 
                request_id, 
                coalesce( min( case when owner_perception != ""
                   then id else null end ), 0 ) minOwnerID,
                coalesce( min( case when tl_perception != ""
                   then id else null end ), 0 ) minTLID,
                MAX(id) AS maxID
             FROM 
                history_gt 
             GROUP BY 
                request_id ) PQ
            on s.request_id = PQ.request_id
             LEFT JOIN history_gt AS j4 
                ON PQ.minOwnerID = j4.id
             LEFT JOIN history_gt AS j6 
                ON PQ.minTLID = j6.id
             LEFT JOIN history_gt AS j2 
                ON PQ.maxID = j2.id
   GROUP BY 
      s.request_id 
   ORDER BY 
      s.id ASC 
   LIMIT 
      50