如何删除复杂 SQL 查询中的某些重复项

Question

我正在编写一个查询，需要它来删除 a.GenUserID 的所有重复项，同时保留最近的登录日期（即 b.LogDateTime），但该日期必须早于 6 个月。如果有更晚的日期，则必须将其删除。我希望这是有道理的。

SELECT DISTINCT 
    a.GenUserID, 
    c.DeletionDate, 
    b.LogDateTime,
    (CASE c.Disabled WHEN 0 THEN 'NO' else 'YES - ARCHIVED' end)
FROM RioReport.dbo.GenUser a 
LEFT JOIN dbo.GenUserArchive c on a.GenUserID = c.GenUserID
LEFT JOIN dbo.GenUserAccessHistory b on a.GenUserID = b.ExtraInfo
WHERE(a.Disabled=0 or c.Disabled=0)
    AND c.DeletionDate IS NOT NULL
    AND ((DateAdd(MM, -6, GetDate()) > b.LogDateTime or b.LogDateTime IS NULL))
ORDER BY a.GenUserID, b.LogDateTime desc

Answer 1

使用cte和window函数

  ;with ctr as (
    select a.GenUserID, a.DeletionDate, a.LogDateTime 
    row_number()over(partition by a.GenUserID order by b.LogDateTime desc) rnk

    from RioReport.dbo.GenUser a )
    select a.GenUserID, a.DeletionDate, a.LogDateTime,
        CASE  WHEN DATEDIFF(mm,LogDateTime,getdate())<6 THEN 'NO' else 'YES - ARCHIVED' end)
     from ctr a where a.rnk=1

Answer 2

您可以将 row_number() 信息添加到您的查询中，并将该查询包装到一个外部查询中，该查询仅从该结果中获取编号为 1 的记录：

select      *
from        (
    select      a.GenUserID, 
                c.DeletionDate, 
                b.LogDateTime,
                case c.Disabled when 0 then 'NO' else 'YES - ARCHIVED' end as diabled,
                row_number() over (partition by a.GenUserID
                                   order by     b.LogDateTime desc) as rn
    from        RioReport.dbo.GenUser a 
    inner join  dbo.GenUserArchive c
            on  a.GenUserID = c.GenUserID
    left join   dbo.GenUserAccessHistory b
            on  a.GenUserID = b.ExtraInfo
    where       (a.Disabled=0 or c.Disabled=0)
    and         c.DeletionDate is not null
    and         (DateAdd(MM, -6, GetDate()) > b.LogDateTime or b.LogDateTime is null)
    )
where       rn = 1            
order by    a.GenUserID

请注意，您可以将第一个 left join 变成 inner join 而无需对结果集进行任何更改，因为您对其其中一个字段进行了非空检查。 inner join 是首选，可能会提高性能。

如果 GenUserAccessHistory.LogDateTime 始终为非空，则可以通过将 DateAdd(MM, -6, GetDate()) > b.LogDateTime 条件移动到适当的连接 on 子句来避免测试 or b.LogDateTime is null。

生成的行号将按照 LogDateTime 值的降序排列，并为每个不同的用户从 1 重新开始。

没有 window 功能的替代方案

自 SQL Server 2008 起支持

row_number() 和其他 window 函数。在您写的评论中您不能使用它。如果是这种情况，这里有一个使用通用 table 表达式的替代方法（自 SQL Server 2005 起支持）：

;with cte as (
    select      a.GenUserID, 
                c.DeletionDate, 
                b.LogDateTime,
                case c.Disabled when 0 then 'NO' else 'YES - ARCHIVED' end as disabled,
    from        RioReport.dbo.GenUser a 
    inner join  dbo.GenUserArchive c
            on  a.GenUserID = c.GenUserID
    left join   dbo.GenUserAccessHistory b
            on  a.GenUserID = b.ExtraInfo
    where       (a.Disabled=0 or c.Disabled=0)
    and         c.DeletionDate is not null
    and         (DateAdd(MM, -6, GetDate()) > b.LogDateTime or b.LogDateTime is null)
    )    
select      *
from        cte main
where       LogDateTime is null
        or  not exists (select   1
                        from     cte sub
                        where    sub.GenUserID = main.GenUserID
                        and      sub.LogDateTime > main.LogDateTime)
order by    GenUserID

Answer 3

尝试使用以下查询。

;WITH CTE_Group
AS(
SELECT 
    ROW_NUMBER() OVER (PARTITION BY a.GenUserID ORDER BY b.LogDateTime DESC) as RNO, 
    a.GenUserID, 
    c.DeletionDate, 
    b.LogDateTime,
    (CASE c.Disabled WHEN 0 THEN 'NO' else 'YES - ARCHIVED' end) IsArchived
FROM RioReport.dbo.GenUser a 
LEFT JOIN dbo.GenUserArchive c on a.GenUserID = c.GenUserID
LEFT JOIN dbo.GenUserAccessHistory b on a.GenUserID = b.ExtraInfo
WHERE(a.Disabled=0 or c.Disabled=0)
    AND c.DeletionDate IS NOT NULL
    AND ((DateAdd(MM, -6, GetDate()) > b.LogDateTime or b.LogDateTime IS NULL)))
    SELECT  GenUserID, 
            DeletionDate, 
            LogDateTime,
            IsArchived
    FROM WITH_CTE_Group
    WHERE RNO=1

如何删除复杂 SQL 查询中的某些重复项

How do I remove certain duplicates in a complex SQL query

sql

tsql

sql-server

greatest-n-per-group

没有 window 功能的替代方案