Question

How do these results make sense? I don’t understand.
Shouldn’t for example the last query return an empty set since that there are no threads with date > 2010? Why does it return a result from 2003?

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

Empty set (0.00 sec)

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

Empty set (0.00 sec)

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 |
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+

1 row in set (0.00 sec)

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 |
+--------------+-----------+-----------+----------+---------------------+---------------------+---------------------------------+-------------------------+

1 row in set (0.00 sec)

Answer 1

You are using wrong type of quotes. MySQL thinks that you are comparing string “thread_date”. Here is how it should be:

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

This way MySQL knows that you mean field thread_date and compares it to the date at the right side of expression.