MariaDB、PBXT和神秘的查询结果

首先，这是表格：

CREATE TABLE `outlet_tags` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `importer_id` int(11) NOT NULL,
  `outlet_id` int(11) NOT NULL,
  `code` varchar(20) NOT NULL,
  `postcode` varchar(15) DEFAULT NULL,
  `tag_set` varchar(45) DEFAULT NULL,
  `tag_type` varchar(45) DEFAULT NULL,
  `tag_details` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `fk_report_outlet_tags_1` (`importer_id`),
  KEY `fk_report_outlet_tags_2` (`outlet_id`),
  KEY `outlet_tag_set` (`tag_set`),
  KEY `outlet_tag_type` (`tag_type`),
  KEY `outlet_tag_details` (`tag_details`),
  CONSTRAINT `fk_report_outlet_tags_1` FOREIGN KEY (`importer_id`) REFERENCES `importers` (`id`),
  CONSTRAINT `fk_report_outlet_tags_2` FOREIGN KEY (`outlet_id`) REFERENCES `outlets` (`id`)
) ENGINE=PBXT DEFAULT CHARSET=utf8;

有人能解释为什么字段值会根据以下查询中使用的条件而变化吗？如果引擎是Maria，就不会发生这种情况

select * from outlet_tags where code=1503 and outlet_id=407 limit 3;
+------+-------------+-----------+------+----------+---------+-----------------+----------------+
| id   | importer_id | outlet_id | code | postcode | tag_set | tag_type        | tag_details    |
+------+-------------+-----------+------+----------+---------+-----------------+----------------+
|  222 |           1 |       407 | 1503 | XXX XXX  | outlet  | Make up         | Make up        |
|  675 |           1 |       407 | 1503 | XXX XXX  | outlet  | Approved Status | Approved       |
| 1619 |           1 |       407 | 1503 | XXX XXX  | outlet  | Retail Area     | No Retail Area |
+------+-------------+-----------+------+----------+---------+-----------------+----------------+
3 rows in set (0.00 sec)

select * from outlet_tags where code=1503 and importer_id=1 limit 3;
+------+-------------+-----------+------+----------+---------+-----------------+----------------+
| id   | importer_id | outlet_id | code | postcode | tag_set | tag_type        | tag_details    |
+------+-------------+-----------+------+----------+---------+-----------------+----------------+
|  222 |           1 |       407 | 1503 | XXX XXX  | outlet  | Make up         | Make up        |
|  675 |           1 |       407 | 1503 | XXX XXX  | outlet  | Approved Status | Approved       |
| 1619 |           1 |       407 | 1503 | XXX XXX  | outlet  | Retail Area     | No Retail Area |
+------+-------------+-----------+------+----------+---------+-----------------+----------------+
3 rows in set (0.00 sec)

select * from outlet_tags where importer_id=1 and outlet_id=407 limit 3;
+------+-------------+-----------+------+----------+---------+----------+-------------+
| id   | importer_id | outlet_id | code | postcode | tag_set | tag_type | tag_details |
+------+-------------+-----------+------+----------+---------+----------+-------------+
|  222 |           1 |       407 | 1503 | NULL     | NULL    | NULL     | NULL        |
|  675 |           1 |       407 | 1503 | NULL     | NULL    | NULL     | NULL        |
| 1619 |           1 |       407 | 1503 | NULL     | NULL    | NULL     | NULL        |
+------+-------------+-----------+------+----------+---------+----------+-------------+
3 rows in set (0.00 sec)

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更新：从MariaDB 5.5开始，尝试在查询中使用ORDER BY

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不同的引擎可能会以不同的顺序返回行，这取决于行的检索方式。

感谢您将这一行从死角带回来！我不确定我是否理解你的评论。3个查询返回的行具有匹配的PK，因此是相同的行，但是第三个查询具有空值，而其他2个查询具有有效数据。有人认为可能是坏索引数据导致了空值吗？第三个查询是唯一在WHERE条件中只使用索引字段的查询