MySQL datetime查询的奇怪问题

Question

这些结果是如何解释的？我不明白。

例如，最后一个查询不应该返回一个空集，因为没有日期为> 2010的线程吗？为什么它会返回2003年的结果？

mysql> SELECT * 
       FROM thread 
       WHERE newsgroup_id = '64654' 
       AND 'thread_date' < '2010-09-10 21:43:05' 
       LIMIT 1;

空集(0.00秒)

mysql> SELECT * 
       FROM thread 
       WHERE newsgroup_id = '64654' 
       AND 'thread_date' < '2000-09-10 21:43:05' 
       LIMIT 1;

空集(0.00秒)

mysql> SELECT * 
       FROM thread 
       WHERE newsgroup_id = '64654' 
       AND 'thread_date' > '2000-09-10 21:43:05' 
       LIMIT 1;
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+
| newsgroup_id | thread_id | postcount | hash     | thread_date         | thread_date_last        | thread_title                    | title_has_valid_charset |
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+
|        64654 |         1 |         0 | O2gvcPRl | 2003-06-06 22:51:24 | 0000-00-00 00:00:00 | Vendo fotodigit  2.1  megapixel |                       0 |
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+

集合中的1行(0.00秒)

mysql> SELECT * 
       FROM thread 
       WHERE newsgroup_id = '64654' 
       AND 'thread_date' > '2010-09-10 21:43:05' 
       LIMIT 1;
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+
| newsgroup_id | thread_id | postcount | hash     | thread_date         | thread_date_last    | thread_title                    | title_has_valid_charset |
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+
|        64654 |         1 |         0 | O2gvcPRl | 2003-06-06 22:51:24 | 0000-00-00 00:00:00 | Vendo fotodigit  2.1  megapixel |                       0 |
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+

集合中的1行(0.00秒)

Answer 1

您使用了错误的引号类型。MySQL认为您正在比较字符串"thread_date“。下面是它应该是什么样子的：

`thread_date` > '2010-09-10 21:43:05'

这样，MySQL就知道您指的是字段thread_date，并将其与表达式右侧的日期进行比较。

Answer 2

'thread_date'是一个字符串，而不是该字段的值。

你的意思是：

`thread_date` > '2010-09-10 21:43:05'