Mysql：根据“关键字”位置搜索数据库

Question

我有下表，标签

+---------+------------------------------+
| tag_id  | tag_name                     |
+---------+------------------------------+
| 1       | test, subject                |
+----------------------------------------+
| 2       | subject, test, this          |
+----------------------------------------+
| 3       | how, is, subject, test, this |
+----------------------------------------+
| 4       | this, is, test, subject      |
+---------+------------------------------+
| 5       | test                         |
+---------+------------------------------+
| 6       | testing, microphone          |
+---------+------------------------------+
| 7       | microphone, this, is a, test |
+---------+------------------------------+

我想搜索关键字test并根据关键字在字段tag_name中的字符串中的位置按相关性对结果进行排序。

所以结果的顺序是5, 1, 6, 2, 4, 3, 7 。

我已经尝试了下面的代码，它几乎可以工作，期待这样一个事实，即 LIKE 'test%' 将按照唯一 ID的顺序返回在字符串中间包含关键字test结果，而不是关键字的位置在字符串中

SELECT *
FROM tags
WHERE `tag_name` LIKE '%test%'
ORDER BY
  CASE
    WHEN `tag_name` LIKE 'test' THEN 1
    WHEN `tag_name` LIKE 'test%' THEN 2
    WHEN `tag_name` LIKE '%test' THEN 4
    ELSE 3
  END

上面的代码将返回以下结果：

+---------+------------------------------+
| tag_id  | tag_name                     |
+---------+------------------------------+
| 5       | test                         |
+---------+------------------------------+
| 1       | test, subject                |
+----------------------------------------+
| 6       | testing, microphone          |
+---------+------------------------------+
| 2       | subject, test, this          |
+----------------------------------------+
| 3       | how, is, subject, test, this |
+----------------------------------------+
| 4       | this, is, test, subject      |
+---------+------------------------------+
| 7       | microphone, this, is a, test |
+---------+------------------------------+

顺序变为5, 1, 6, 2, 4, 3, 7而不是5, 1, 6, 2, 3, 4, 7

如何根据 LIKE 'test%' 的关键字位置返回结果，或者是否有更好的方法来实现？

谢谢！

Answer 1

您也可以在ORDER BY上使用LOCATE使用以下解决方案：

SELECT *
FROM tags
WHERE `tag_name` LIKE '%test%'
ORDER BY CAST(`tag_name` LIKE 'test' AS UNSIGNED) DESC,
  CAST(`tag_name` LIKE '%test%' AS UNSIGNED) ASC,
  LOCATE('test', `tag_name`) ASC

您可以使用此查询调试上述查询。 在那里您可以看到ORDER BY值：

SELECT *,
  CAST(`tag_name` LIKE 'test' AS UNSIGNED) AS KeywordOnly,
  CAST(`tag_name` LIKE '%test%' AS UNSIGNED) AS KeywordExists,
  LOCATE('test', `tag_name`) AS KeywordPosition
FROM tags
WHERE `tag_name` LIKE '%test%'
ORDER BY CAST(`tag_name` LIKE 'test' AS UNSIGNED) DESC,
  CAST(`tag_name` LIKE '%test%' AS UNSIGNED) ASC,
  LOCATE('test', `tag_name`) ASC

dbfiddle.uk 上的演示