加入 2 个表时重复

Question

我有一个包含大量数据的 Select 语句，超过 23K，它与超过 5 个 table 结合在一起，当我查看 table 我看到我正在做的连接有 2 行匹配，

我试过按 Group by 但没用，我也试过 Select DISTINCT 但也没用，我该怎么做？

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

返回重复项是因为 tbInterview 有多个采访链接了 USerID，然后我尝试了这个

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 ''

这个也没用。

这是 table 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，当我对 tbInterview 执行 Select 连接时，它显示输出如下： ╔═══════════╤══════════╤═════════════════════════════╗ ║ FirstName │ LastName │ Interview ║ ╠═══════════╪══════════╪═════════════════════════════╣ ║ James │ Smith │ Inter View Done ║ ╟───────────┼──────────┼─────────────────────────────╢ ║ James │ Smith │ 2nd Interview was requested ║ ╚═══════════╧══════════╧═════════════════════════════╝

Answer 1

假设您要在 tbInterview 中查找最新创建日期的行，那么您有几种可能的解决方案。这是一个基于您的第一个查询的与 ROWNUMBER() 函数一起使用的函数：

这假设您实际上只需要 CreatedDate 值（假设在 tbData table 上，因为 DateCreated 在 tbInterview 上被命名为等效值）在示例中指定的范围内的信息查询。

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。

加入 2 个表时重复

Duplicates on joining 2 tables

sql-server

select

distinct

left-join

duplicates