Question

So basically I have two tables:

u_contracts

+--------+---------+------------------------------+
| id     | user_id | reschedule_wait_confirm_till |
+--------+---------+------------------------------+
| 107742 |   19982 | 2012-08-08 17:10:41          |
|  38548 |    4622 | 2012-08-08 10:24:42          |
|  98483 |   36707 | 2012-08-08 21:39:08          |
|  45165 |   17632 | 2012-08-08 23:13:57          |
| 131285 |   47527 | 2012-08-08 08:33:58          |
| 131686 |   40194 | 2012-08-08 12:18:09          |
|  91749 |   11021 | 2012-08-08 12:22:05          |
+--------+---------+------------------------------+

restruct_mail_history

+----+---------+---------------------+
| id | user_id | _date               |
+----+---------+---------------------+
|  1 |   47527 | 2012-08-07 12:16:51 |
+----+---------+---------------------+

现在，我需要从u_contracts中选择明天有reschedule_wait_confirm_till日期的所有user_id，并且restruct_mail_history中没有今天的用户。

到目前为止，我有一个像这样的工作查询：

SELECT
  uc.user_id
FROM
  u_contracts uc
WHERE
  uc._status = 6
  AND DATE( uc.reschedule_wait_confirm_till ) = DATE( ADDDATE( now(), 1 ) )
  AND uc.user_id NOT IN ( SELECT rmh.user_id FROM restruct_mail_history rmh WHERE DATE( rmh._date ) = DATE( now() ));

输出：

现在我不喜欢WHERE中的SELECT语句，所以我计划像这样进行LEFT JOIN：

SELECT
  uc.user_id
FROM
  u_contracts uc
LEFT JOIN
  restruct_mail_history rmh
ON
  uc.user_id = rmh.user_id
WHERE
  uc._status = 6
  AND DATE( uc.reschedule_wait_confirm_till ) = DATE( ADDDATE( now(), 1 ) );

输出：

现在这给了我所有的u_contracts结果，但是当我添加必要的参数AND DATE( rmh._date ) != DATE( now() )时，它给了我绝对的结果。

知道我做错了吗？

编辑如果iI将最后一行更改为AND DATE( rmh._date ) = DATE( now() )，它只会向我提供不应该在列表中的结果，这是正确的。为什么它不相反？

谢谢你。

Answer 1

试试这个：

SELECT uc.user_id
FROM u_contracts uc
     LEFT JOIN restruct_mail_history rmh
        ON uc.user_id = rmh.user_id
WHERE uc._status = 6 AND
      DATE( uc.reschedule_wait_confirm_till ) = DATE( ADDDATE( now(), 1) ) AND
      (rmh.user_id IS NULL OR DATE( rmh._date ) != DATE( now() ));

见这里：Visual Explanation Of Joins.

Answer 2

试试这个

SELECT 
  uc.user_id 
FROM 
  u_contracts uc 
LEFT JOIN 
  restruct_mail_history rmh 
ON 
  uc.user_id = rmh.user_id and   uc._status = 6 
  AND DATE( uc.reschedule_wait_confirm_till ) = DATE( ADDDATE( now(), -147 ) );

LEFT JOIN没有结果

2 个答案: