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我有一个人员表、一个单位表和一个健康表（如下所述）。基本上在我的工作中，我们必须检查人员，如果他们已经两天没有出现，我们就会去寻找他们......我想要的是能够从健康表中选择所有记录超过两天，但只有最新的（因为每人每天可能会有多个条目，这就是我想要的，因为通过该wellness.username字段您可以知道谁看到了谁，何时看到）。

People 
+------------+-------------+------+-----+-------------------+----------------+
| Field      | Type        | Null | Key | Default           | Extra          |
+------------+-------------+------+-----+-------------------+----------------+
| id         | int(11)     | NO   | PRI | NULL              | auto_increment |
| fname      | varchar(32) | NO   |     | NULL              |                |
| lname      | varchar(32) | NO   |     | NULL              |                |
| dob        | date        | NO   |     | 0000-00-00        |                |
| license_no | varchar(24) | NO   |     | NULL              |                |
| date_added | timestamp   | NO   |     | CURRENT_TIMESTAMP |                |
| status     | varchar(8)  | NO   |     | Allow             |                |
+------------+-------------+------+-----+-------------------+----------------+

Units
+----------+-------------+------+-----+---------+----------------+ 
| Field    | Type        | Null | Key | Default | Extra          |
+----------+-------------+------+-----+---------+----------------+
| id       | int(11)     | NO   | PRI | NULL    | auto_increment |
| number   | varchar(3)  | NO   |     | NULL    |                |
| resident | int(11)     | NO   | MUL | NULL    |                |
| type     | varchar(16) | NO   |     | NULL    |                |
+----------+-------------+------+-----+---------+----------------+

+--------------+-------------+------+-----+-------------------+----------------+
| Field        | Type        | Null | Key | Default           | Extra          |
+--------------+-------------+------+-----+-------------------+----------------+
| wellness_id  | int(11)     | NO   | PRI | NULL              | auto_increment |
| people_id    | int(11)     | NO   |     | NULL              |                |
| time_checked | timestamp   | NO   |     | CURRENT_TIMESTAMP |                |
| check_type   | varchar(1)  | NO   |     | NULL              |                |
| username     | varchar(16) | NO   |     | jmd9qs            |                |
+--------------+-------------+------+-----+-------------------+----------------+

这张units桌子很丑，我知道，但很快就会改变；就目前而言，resident引用people.id.

people这是我的最小工作示例，即使有多个连续超过 2 天的结果，它也只会给我一个wellness结果time_checked。我得到的一个结果更像是 4-1/2 天大....

select w.wellness_id, p.id, p.lname, p.fname, u.number, u.type,
w.time_checked, w.check_type, w.username 
from people p 
    left join units u on p.id = u.resident
    right join wellness w on p.id = w.people_id 
    WHERE w.time_checked <= DATE_ADD(CURDATE(), INTERVAL -2 DAY)
order by w.time_checked asc;

我正在尝试获取超过两天的最新记录，但表people中只有 1 条wellness。我加入了所有其他的东西，因为我需要它来用 PHP 显示记录。

抱歉我的问题很杂乱，希望它足够清楚！

编辑 - 样本数据：

+------+------+--------+---------------------+------------+----------+
| w_id | id   | number | time_checked        | check_type | username |
+------+------+--------+---------------------+------------+----------+
|  100 |    2 | 425    | 2013-08-23 21:03:00 | s          | jmd9qs   |
|  101 |    2 | 425    | 2013-08-25 05:41:01 | s          | jmd9qs   |
|   91 |    2 | 425    | 2013-08-20 19:52:23 | s          | jmd9qs   |
|   83 |    4 | 416    | 2013-08-23 20:12:29 | s          | jmd9qs   |
|   76 |    5 | 408    | 2013-08-23 20:11:21 | s          | jmd9qs   |
|   62 |    6 | 327    | 2013-08-23 20:06:13 | s          | jmd9qs   |
|   18 |    7 | 204    | 2013-08-23 19:43:58 | s          | jmd9qs   |
|   31 |    8 | 219    | 2013-08-23 19:51:11 | s          | jmd9qs   |
|   97 |    9 | 432    | 2013-08-23 20:16:39 | o          | jmd9qs   |
|   44 |   10 | 309    | 2013-08-23 19:55:45 | s          | jmd9qs   |
+------+------+--------+---------------------+------------+----------+
4

2 回答 2

2

恕我直言RIGHT JOIN，从people到wellness没有意义，因为不应该出现当你有一个人wellness但没有那个人在people桌子上的情况。但反之亦然。您有一个新人，但还没有关于他或她的任何健康信息。

话虽如此，您的查询可能看起来像这样

SELECT z.wellness_id, p.id, z.time_checked, z.check_type, z.username 
  FROM people p JOIN units u
    ON p.id = u.resident  LEFT JOIN
(
  SELECT w.*
    FROM
  (
    SELECT people_id, MAX(time_checked) time_checked
      FROM wellness
     GROUP BY people_id
  ) q JOIN wellness w 
      ON q.people_id = w.people_id
     AND q.time_checked = w.time_checked
) z 
    ON p.id = z.people_id
 WHERE COALESCE(time_checked, 0) < CURDATE() - INTERVAL 2 DAY

这是SQLFiddle演示

于 2013-08-26T07:02:09.280 回答
1

这是得到我想要的查询：

select p.id, u.number,
    w.time_checked, w.check_type, w.username 
    from people p inner join units u on p.id = u.resident
    left join wellness w on p.id = w.people_id 
    left outer join wellness as w2 ON w.people_id = w2.people_id
    and w.time_checked < w2.time_checked
    where w2.people_id is null and w.time_checked  < (NOW() - INTERVAL 2 DAY)
order by w.time_checked asc
于 2013-08-26T06:52:55.927 回答