Question

我有一个Select语句，其中包含超过23K的大量数据，它与5个以上的表连接在一起，当我查看该表时，其中之一导致重复，我发现我正在执行的连接具有2行匹配，< / p>

我尝试按分组方式进行操作，但没有成功，我还尝试了选择DISTINCT，但同样行不通，我将如何处理？

SELECT DISTINCT FirstName, LastName, F.Interview  FROM tbData D
LEFT JOIN tbInterview F on D.UserID = F.UserID
 where CreatedDate is between '' and ''

因为tbInterview有多个链接USerID的Interview，所以返回Duplicates，然后尝试了

SELECT DISTINCT FirstName, LastName, F.Interview  FROM tbData D
LEFT JOIN (Select UserID from tbInterview GROUP BY UserID) as InterviewID ON D.UserID = InterviewID.UserID
LEFT JOIN tbInterview F on InterviewID.UserID = F.UserID
 where CreatedDate is between '' and ''

这也不起作用。

这是表tbInterview中的数据示例 ╔═════════════╤════════╤═════════════╤═════════════════════════════╗ ║ InterViewID │ UserID │ DateCreated │ Interview ║ ╠═════════════╪════════╪═════════════╪═════════════════════════════╣ ║ 1 │ 120 │ 2015/05/10 │ Inter View Done ║ ╟─────────────┼────────┼─────────────┼─────────────────────────────╢ ║ 2 │ 120 │ 2015/05/15 │ 2nd Interview was requested ║ ╚═════════════╧════════╧═════════════╧═════════════════════════════╝

现在，当我使用tbInterview的Join进行Select时，它显示的输出如下： ╔═══════════╤══════════╤═════════════════════════════╗ ║ FirstName │ LastName │ Interview ║ ╠═══════════╪══════════╪═════════════════════════════╣ ║ James │ Smith │ Inter View Done ║ ╟───────────┼──────────┼─────────────────────────────╢ ║ James │ Smith │ 2nd Interview was requested ║ ╚═══════════╧══════════╧═════════════════════════════╝

Answer 1

假设您正在tbInterview中查找创建日期的最新行，那么您有几种可能的解决方案。这是根据您的第一个查询使用ROWNUMBER（）函数的函数：

这假设您实际上只希望获得示例查询中指定的范围内的信息，该值的范围在CreatedDate值（假设在tbData表上，因为DateCreated在tbInterview上等效）。

SELECT 
    FirstName, 
    LastName, 
    F.Interview
FROM tbData D
LEFT JOIN (
    SELECT 
        UserID,
        CreatedDate,
        ROW_NUMBER() OVER (Partition By UserId ORDER BY DateCreated Desc) as RowNumber
    FROM tbInterview F
    WHERE DateCreated > '' --- Earliest date created for range on tbData
    ) as F
    on D.UserID = F.UserID
WHERE CreatedDate is between '' and '' 
    AND RowNumber = 1

这会将最新的采访行（基于DateCreated）与tbData用户相关联。

联接2个表时重复

1 个答案: