SQL SELECT WHERE NOT IN来自同一个表查询

Question

我遇到以下SQL查询和MySQL的问题

SELECT
  id, cpid, label, cpdatetime
FROM
  mytable AS a
WHERE
  id NOT IN
  (
    SELECT
      id
    FROM
      mytable AS b
    WHERE
      a.label = b.label
    AND
      a.cpdatetime > b.cpdatetime
  )
AND
  label LIKE 'CB%'
AND
  cpid LIKE :cpid
GROUP BY label
ORDER BY cpdatetime ASC

表格看起来像这样

1 | 170.1 | CB55 | 2013-01-01 00:00:01
2 | 135.5 | CB55 | 2013-01-01 00:00:02
3 | 135.6 | CB59 | 2013-01-01 00:00:03
4 | 135.5 | CM43 | 2013-01-01 00:00:04
5 | 135.5 | CB46 | 2013-01-01 00:00:05
6 | 135.7 | CB46 | 2013-01-01 00:00:06
7 | 170.2 | CB46 | 2013-01-01 00:00:07

我希望我的查询返回

3 | 135.6 | CB59
5 | 135.5 | CB46

编辑

标签是狗/猫,而cpids是保持狗/猫的临时家庭.

狗/猫从家庭移动到家庭.

我需要找到位于:userinput系列中的狗/猫,但前提是他们不在另一个家庭中

我无法改变数据库,只需按原样处理数据,而我不是编写应用程序/数据库模式的人.

Answer 1

尝试使用以下方法避免相关的子查询LEFT JOIN:

SELECT a.id, a.cpid, a.label, a.cpdatetime
FROM mytable AS a
LEFT JOIN mytable AS b ON a.label = b.label AND a.cpdatetime > b.cpdatetime
WHERE a.label LIKE 'CB%' AND a.cpid LIKE :cpid
  AND b.label IS NULL
GROUP BY a.label
ORDER BY a.cpdatetime ASC

小提琴

如果连接条件失败,则第二个表别名的字段b将设置为NULL.

或者,使用非相关子查询:

SELECT a.id, a.cpid, a.label, a.cpdatetime
FROM mytable AS a
INNER JOIN (
  SELECT label, MIN(cpdatetime) AS cpdatetime
  FROM mytable
  WHERE label LIKE 'CB%'
  GROUP BY label
) AS b ON a.label = b.label AND a.cpdatetime = b.cpdatetime
WHERE a.cpid LIKE '135%'
ORDER BY a.cpdatetime

首先,您找到cpdatetime每个标签的最小值,然后将其与添加附加cpid条件的第一个表连接.