Question

嗨，我在显示查询代码中的数据时遇到问题。我想显示最近日期的数据。下面是我要显示的示例数据和输出数据。

Landing Area data

|landing_id| id_number| address |
---------------------------------
|    1     | 00012345 | Ozamiz  |
|    2     | 00012346 | Tudela  |
|    3     | 00012347 | Nailon  |
|    4     | 00012348 | Taboo   |
|    5     | 00012349 | Jimenez |
|    6     | 00012350 | Tangub  |
---------------------------------

Percentage data

|percent_id| landing_id | percentage |     date_added     |
-----------------------------------------------------------
|    1     |     1      |     9      |2018-10-08 21:42:22 |
|    2     |     1      |    12      |2018-10-03 20:43:32 |
|    3     |     1      |    43      |2018-10-15 19:43:49 |
|    4     |     3      |    22      |2018-10-10 15:43:56 |
|    5     |     3      |    77      |2018-10-12 18:44:03 |
-----------------------------------------------------------

这是我的查询代码。

SELECT fish_landing.landing_id, 
    percentage.landing_id as percentage_landing_id, 
    percentage.percentage, 
    percentage.date_added 
FROM percentage 
RIGHT OUTER JOIN fish_landing ON percentage.landing_id = fish_landing.landing_id 
ORDER BY fish_landing.landing_id ASC

我的代码的输出是这样，其中date_add和百分比不准确。

|percent_id| percentage |     date_added     |
----------------------------------------------
|    1     |     9      |2018-10-08 21:42:22 |
|    2     |            |                    |
|    3     |    22      |2018-10-10 15:43:56 |
|    4     |            |                    |
|    5     |            |                    |
|    6     |            |                    |
----------------------------------------------

我要显示的输出数据是下表，其中将显示每个landing_id中具有最新date_add的百分比。

|landing_id| percentage |     date_added     | address |
--------------------------------------------------------
|    1     |     43     |2018-10-15 19:43:49 | Ozamiz  |
|    2     |            |                    |         |
|    3     |     77     |2018-10-12 18:44:03 | Nailon  |
|    4     |            |                    |         |
|    5     |            |                    |         |
|    6     |            |                    |         |
--------------------------------------------------------

希望您能为我解决问题。

Answer 1

您可以在单独的派生表中获得一个着陆ID的最大date_added，并将其用于加入。

尝试以下操作：

SELECT fish_landing.landing_id, 
       percentage.percentage, 
       percentage.date_added, 
       fish_landing.address  
FROM fish_landing 
LEFT JOIN percentage ON percentage.landing_id = fish_landing.landing_id 
LEFT JOIN (SELECT landing_id, MAX(date_added) AS max_date_added 
            FROM percentage 
            GROUP BY landing_id) AS dt 
  ON dt.landing_id = percentage.landing_id AND 
     dt.max_date_added = percentage.date_added
ORDER BY fish_landing.landing_id ASC

如何查询最接近的日期并显示特定数据

1 个答案: