Question

大家下午好！我已经在这方面工作了两天，并且不知道为什么这不起作用。我已经尝试了几种不同的方法来获得正确的结果，我要么有太多的回报或0.我有两个表用于跟踪资产，具有以下布局：

表：AssetManagment

id | serial | idcode
---|--------|-------
1  | 123    | 4
2  | 1234   | 4

表：AssetManagement_History

id | rowID  | action    | occurred
---|--------|-----------|-------------
1  | 1      | shipping  | 2014-04-01
2  | 1      | stocked   | 2014-04-02
3  | 1      | installed | 2014-04-03
4  | 2      | stocked   | 2014-04-04

在此示例中，AssetManagement_History.rowID与AssetManagment.id相关，因此您可以看到第一个资产有三个历史详细信息，第二个资产只有一个。我需要返回 last 操作对应于'stocked'或'restocked'的所有资产 - 因此只应返回第二个资产。这是我尝试过的几个mySQL语句：

SELECT tblASSET.id,tblASSET.serial
FROM AssetManagement tblASSET
INNER JOIN 
(SELECT occurred,max(id) id 
FROM AssetManagement_History GROUP BY occurred) tblAH ON tblASSET.id = tblAH.rowID
WHERE tblASSET.idcode='4' AND tblAH.action IN ('stocked','restocked')

另一次尝试：

SELECT tblASSET.id,tblASSET.serial
FROM AssetManagement tblASSET
INNER JOIN 
(SELECT max(rowID) rowID 
FROM AssetManagement_History GROUP BY occurred) tblAH ON tblAH.rowID = tblASSET.id
WHERE tblASSET.idcode='4'

我还有其他几个，但他们也没有工作。非常感谢任何帮助！

谢谢，戴夫

Answer 1

SELECT
    A.id,
    A.serial
FROM AssetManagement A

INNER JOIN ( -- Join to get our latest history ID
  SELECT
      H.rowID,
      MAX(H.ID) ID
  FROM AssetManagement_History H
  GROUP BY H.rowID
) H1
ON H1.rowID = A.id

INNER JOIN AssetManagement_History H2 -- Join to get the row for the latest history
ON H2.ID = H1.ID

WHERE
  H2.action IN ('stocked', 'restocked')
  AND
  A.IDCode = 4

Answer 2

SELECT tblASSET.id,tblASSET.serial
FROM AssetManagement AS tblASSET
INNER JOIN AssetManagement_History AS tblAH
 ON tblAH.rowID = tblASSET.id
WHERE tblASSET.idcode='4'

您收到了哪些错误消息？您希望结果如何？

Answer 3

尝试使用NOT EXISTS，（解释在评论中）

SELECT tblASSET.id, tblASSET.serial
FROM AssetManagment AS tblASSET
    INNER JOIN AssetManagement_History AS tblAH
       ON tblAH.rowID = tblASSET.id
WHERE tblASSET.idcode = '4' 
    AND tblAH.action IN ('stocked','restocked')
    --/*And not exists occurred that is greater for the same rowID*/
    AND NOT EXISTS (SELECT 1 FROM AssetManagement_History AS his
                WHERE his.rowID = tblAH.rowID 
                    AND his.occurred > tblAH.occurred )

编辑：修改了查询中的错误，这是一个有效的SQL FIDDLE。

Answer 4

这是一个格式化的评论而不是答案

此：

INNER JOIN 
(SELECT occurred,max(id) id 
FROM AssetManagement_History GROUP BY occurred) tblAH ON tblASSET.id = tblAH.rowID

会抛出错误，因为tblAH没有名为rowID的字段。这样：

INNER JOIN 
(SELECT max(rowID) rowID 
FROM AssetManagement_History GROUP BY occurred) tblAH ON tblAH.rowID = tblASSET.id

由于你的愚蠢子查询，

可能会给出奇怪的结果。您正在按照您未选择的字段进行分组。单独运行该子查询，看它是否返回您期望的结果。

Answer 5

我认为这就是你要找的东西。您需要对子查询中的操作应用where子句。

SELECT tblASSET.id,tblASSET.serial
  FROM AssetManagement tblASSET
 INNER JOIN (SELECT occurred,max(id) id
               FROM AssetManagement_History
              where action in IN ('stocked','restocked') GROUP BY occurred
            ) tblAH ON tblASSET.id = tblAH.id
WHERE tblASSET.idcode='4'

INNER JOIN没有返回结果

5 个答案: