Question

我有两个表，MachineWiseMaterial（字段：McMatID）和MaterialIssueRegister（字段：McMatID，IssueDate，IssueTime，EMR）。我想要每个McMatID的最后一期日期，时间和EMR。

对于任何使用SELECT TOP 1的McMatID，我都能找到相同的内容，如下所示。

SELECT TOP 1 McMatID, IssueDate, IssueTime, EMR 
FROM MaterialIssueRegister 
WHERE McMatID = [some value, eg. 1] 
ORDER BY IssueDate DESC, IssueTime DESC, EMR DESC;

但是当我试图加入这两张牌桌时，我没有得到理想的结果。

SELECT MachineWiseMaterial.McMatID, b.IssueDate, b.EMR 
FROM MachineWiseMaterial 
LEFT JOIN (SELECT TOP 1 McMatID, IssueDate, IssueTime, EMR 
FROM MaterialIssueRegister  
ORDER BY IssueDate DESC, IssueTime DESC, EMR DESC) AS b
ON MachineWiseMaterial.McMatID = b.McMatID;

上述查询仅返回IssueDate为Max的McMatID，而不是每个McMatID的最大日期。

Answer 1

你可以尝试这样......

SELECT MachineWiseMaterial.McMatID, b.IssueDate, b.EMR 
FROM MachineWiseMaterial m1
where m1.McMatId=(SELECT TOP 1 McMatID
FROM MaterialIssueRegister  m2
where m2.McMatId=m1.McMatId
ORDER BY IssueDate DESC, IssueTime DESC, EMR DESC)

Answer 2

这样的事情：

选择MachineWiseMaterial.McMatID，b.EMR，max（b.IssueDate）来自MachineWiseMaterial LEFT JOIN MaterialIssueRegister b ON MachineWiseMaterial.McMatID = b.McMatID group by MachineWiseMaterial.McMatID，b.EMR

加入两个表，这样只能连接第二个表中的一行

2 个答案: