Question

我有一个名为sw_sowing

的表

-----------------------------------------------------------------
 id  |   id_unit  |  date      |  id_variety |  type  |  status |
-----------------------------------------------------------------
  1  |      1     | 2017-08-10 |     1        |  SW   |    200  |
-----------------------------------------------------------------
  2  |      1     | 2017-10-10 |     1        |  ER   |    100  |
-----------------------------------------------------------------
  3  |      1     | 2017-11-30 |     2        |  SW   |    100  |
-----------------------------------------------------------------
  4  |      2     | 2017-12-10 |     3        |  SW   |    200  |
-----------------------------------------------------------------
  5  |      2     | 2017-12-10 |     3        |  ER   |    100  |
-----------------------------------------------------------------
  6  |      3     | 2017-08-05 |     4        |  SW   |    200  |
-----------------------------------------------------------------
  7  |      3     | 2017-12-13 |     4        |  ER   |    100  |
-----------------------------------------------------------------
  8  |      3     | 2018-01-04 |     1        |  SW   |    100  |
-----------------------------------------------------------------
  9  |      3     | 2018-01-04 |     2        |  SW   |    100  |
-----------------------------------------------------------------

我想知道id_unit的当前状态和id_variety（取决于日期）。我有这个查询：

SELECT sw_sowing.id_unit, sw_sowing.id_variety, sw_sowing.type, sw_sowing.status
FROM (
        SELECT MAX(id) AS id
        FROM sw_sowing
        WHERE date <= '2018-09-06'
        GROUP BY id_unit
) AS sw
INNER JOIN sw_sowing ON sw_sowing.id = sw.id

它给我以下结果：

----------------------------------------------------- 
   id_unit  |    id_variety |    type    |   status |
-----------------------------------------------------
      1     |        2      |     SW     |    100   |
-----------------------------------------------------
      2     |        3      |     ER     |    100   |
-----------------------------------------------------
      3     |        2      |     SW     |    100   |
-----------------------------------------------------

问题是id_unit = 3与id_variety有两个不同的state = 100，但是前一个查询给出了最后一个，而我想要两个id_variety。

类似这样的东西：

----------------------------------------------------- 
   id_unit  |    id_variety |    type    |   status |
-----------------------------------------------------
      1     |        2      |     SW     |    100   |
-----------------------------------------------------
      2     |        3      |     ER     |    100   |
-----------------------------------------------------
      3     |        1      |     SW     |    100   |
-----------------------------------------------------
      3     |        2      |     SW     |    100   |
-----------------------------------------------------

我希望你能帮助我！

Answer 1

只需在GROUP BY上包含id_variety。

    SELECT sw_sowing.id_unit, sw_sowing.id_variety, sw_sowing.type, sw_sowing.status
FROM (
        SELECT MAX(id) AS id
        FROM sw_sowing
        WHERE date <= '2018-09-06'
        GROUP BY id_unit,id_variety
) AS sw
INNER JOIN sw_sowing ON sw_sowing.id = sw.id

Answer 2

我不知道您为什么有此要求，但我认为您可以使用以下查询来实现：

SELECT id_unit, id_variety, type, status FROM sw_sowing WHERE id IN (
  SELECT MAX(id) FROM sw_sowing WHERE (id_unit, date) IN (
    SELECT id_unit, MAX(date) FROM sw_sowing 
    WHERE date <= '2018-09-06'
    GROUP BY id_unit)
  GROUP BY id_unit, id_variety)

希望这会有所帮助。

通过组mysql获取最大ID

2 个答案: