在外键上选择不同的，内连接另一个表

Question

基本上我想做的是，选择用户最后的 3 个操作。但是 RelationId 上没有重复项，并且还有 innerjoin 权限，只是为了确保用户仍然有权执行相同的操作。

我唯一想要的权限是 RelationId。

没有重复我的意思是如果有两行具有相同 RelationId 的 Action 应该选择靠近顶部的那一行（按 TimeStamp 排序）。

到目前为止我想出了什么：

SELECT DISTINCT a.*, p.RelationId
FROM [Action] [a]
INNER JOIN [Permission] p 
  ON ([p].[RelationId] = [a].[RelationId] 
  AND [p].[RelationType] = [a].[RelationType] 
  AND [p].[UserId] = [a].[UserId] 
  AND [p].[Deleted] = 0)
WHERE [a].[ActionType] = 'Clicked' 
AND [a].[RelationType] = 'Direct' 
AND [a].[UserId] = 5 
AND [a].[Deleted] = 0
ORDER BY [a].[TimeStamp] DESC
OFFSET 0 ROWS
FETCH NEXT 3 ROWS ONLY

分页只需要使用OFFSET X ROWS和FETCH NEXT 3 ROWS

由于某种原因，这不起作用，因为我在 RelationId 上得到了重复项。 没有错误。

示例数据：

action (
    id            INTEGER       PRIMARY KEY,
    ActionType    VARCHAR(50)   not null,
    RelationId    INTEGER       ForeignKey,
    Deleted       Bit           not null,
    TimeStamp     DATE          not null,
    UserId        INTEGER       ForeignKey
);

期望的结果：一个用户执行的最后 3 次操作，该用户具有不同的 RelationId 权限。

Answer 1

根据您对每个用户最后 3 个的定义（如果最后 3 个，则每个关系 ID 不能是单行）：

with data as (
  SELECT *, 
  row_number() over (partition by relationId order by [timeStamp] desc) as rNo
  from action 
  where [ActionType] = 'Clicked' AND 
        [RelationType] = 'Direct' AND 
        [UserId] = 5 AND 
        [Deleted] = 0
)
select a.id,a.ActionType,a.RelationId,a.Deleted,a.TimeStamp,a.UserId,
       p.RelationId as pRelId
FROM [data] [a]
INNER JOIN [Permission] p ON ([p].[RelationId] = [a].[RelationId] AND [p].[RelationType] = [a].[RelationType] AND [p].[UserId] = [a].[UserId]) 
WHERE p.[Deleted] = 0 and a.rNo <= 3
ORDER BY [a].[TimeStamp] DESC;

Answer 2

如果我明白了，您只需要为每个 Permission 提供最新的操作，并从所有这些中保留最近的三行。这里：

select top 3 p.RelationId,top_action.*
from 
    [Permission] p
    cross apply
    (
        select top 1 *
        from [Action] [a]
        where 
            [p].[RelationId] = [a].[RelationId] AND [p].[RelationType] = [a].[RelationType] AND [p].[UserId] = [a].[UserId] 
            and [a].[ActionType] = 'Clicked' AND [a].[RelationType] = 'Direct' AND [a].[UserId] = 5 AND [a].[Deleted] = 0
        order by [a].[TimeStamp] DESC
    )top_action
where [p].[Deleted] = 0
order by top_action.[TimeStamp] DESC

Answer 3

Distinct 将始终区分所有参数。选择 * 总是不同的。 您只需选择一个参数即可确定。

您可以使用 group by，也可以使用相同的选择分两步进行分组。像这样：

select * from Action where id in (
SELECT DISTINCT a.id
FROM [Action] [a]
INNER JOIN [Permission] p 
  ON ([p].[RelationId] = [a].[RelationId] 
  AND [p].[RelationType] = [a].[RelationType] 
  AND [p].[UserId] = [a].[UserId] 
  AND [p].[Deleted] = 0)
WHERE [a].[ActionType] = 'Clicked' 
AND [a].[RelationType] = 'Direct' 
AND [a].[UserId] = 5 
AND [a].[Deleted] = 0
ORDER BY [a].[TimeStamp] DESC
OFFSET 0 ROWS
FETCH NEXT 3 ROWS ONLY
)

Answer 4

通过这样做解决了它。不知道这是否是最好的解决方案。

SELECT [a].*, [p].[Id]
FROM (SELECT *, ROW_NUMBER() OVER(PARTITION BY [RelationId] ORDER BY [TimeStamp] DESC) AS row from [Action]) a
INNER JOIN [Permission] p ON ([ep].[RelationId] = [a].[RelationId] AND [p].[RelationType] = [a].[RelationType] AND [p].[UserId] = [a].[UserId] AND [p].[Deleted] = 0)
WHERE row = 1 AND [a].[ActionType] = 'Clicked' AND [a].[RelationType] = 'Direct' AND [a].[UserId] = 5 AND [a].[Deleted] = 0
ORDER BY [a].[TimeStamp] DESC
OFFSET 0 ROWS
FETCH NEXT 3 ROWS ONLY