Erik提出的问题 -dba

Erik

Asked: 2018-12-04 11:01:49 +0800 CST

像这样拼接一个字符串会让我面临 SQL 注入吗？

3

我最近用以下代码示例回答了一个问题：

Create Table #Testing
(
  emaildomain varchar(100) -- Still bigger than functionally needed but better than MAX
);
INSERT INTO #Testing VALUES (REVERSE('@myfreepaysite.com')); -- Changed


Create Table #DataToCheck
(
  fullemail varchar(200) -- Still bigger than functionally needed but better than MAX
);
Insert Into #DataToCheck VALUES(REVERSE('[email protected]')); --Changed

Select Top 1 
  REVERSE(fullemail)
  , REVERSE(emaildomain)
FROM #DataToCheck
  INNER JOIN #Testing ON fullemail LIKE emaildomain + '%';

在我写最后一行时，我想知道EmailDomain用通配符连接列是否为 SQL 注入打开了大门。这是我应该注意这种类型的代码，还是 SQL Server 会将其评估为单个统一参数，这样我就不必担心使用这种方法？

Erik

Asked: 2016-12-07 12:18:24 +0800 CST

我应该警惕 ON DUPLICATE KEY UPDATE 吗？

2

我是 MySQL 的新手，但我对 SQL Server 有一定的经验。我知道在 SQL Server 中我应该非常谨慎地使用MERGE语句，因为它们会导致一些问题。使用时有什么特别需要注意的ON DUPLICATE KEY UPDATE吗？像在 SQL Server 中那样坚持使用单独的INSERT/UPDATE语句是否被认为是 MySQL 社区的最佳实践，或者ON DUPLICATE KEY UPDATE广泛用于简单的更新插入是否合适？

Erik

Asked: 2016-05-06 14:29:32 +0800 CST

与交易计数相关的规则

4

我正在阅读MSDN上的TRY-CATCH块示例。

示例B的代码清单如下：

BEGIN TRANSACTION;

BEGIN TRY
    -- Generate a constraint violation error.
    DELETE FROM Production.Product
    WHERE ProductID = 980;
END TRY
BEGIN CATCH
    SELECT 
        ERROR_NUMBER() AS ErrorNumber
        ,ERROR_SEVERITY() AS ErrorSeverity
        ,ERROR_STATE() AS ErrorState
        ,ERROR_PROCEDURE() AS ErrorProcedure
        ,ERROR_LINE() AS ErrorLine
        ,ERROR_MESSAGE() AS ErrorMessage;

    IF @@TRANCOUNT > 0
        ROLLBACK TRANSACTION;
END CATCH;

IF @@TRANCOUNT > 0
    COMMIT TRANSACTION;
GO

我不明白的是为什么他们会费心去检查街区@@TRANCOUNT。CATCH在此代码段中，交易计数是否真的有可能 < 1，或者保护条款只是例子应该是示例原则的示例？

Erik

Asked: 2015-11-12 08:04:11 +0800 CST

为什么 TVP 必须是 READONLY，其他类型的参数为什么不能是 READONLY

21

根据此博客，函数或存储过程的参数如果不是参数，则本质上是按值传递，如果它们是OUTPUT参数，则本质上被视为更安全的按引用传递版本OUTPUT。

起初我以为强制声明 TVP 的目的是READONLY向开发人员明确表明 TVP 不能用作OUTPUT参数，但肯定还有更多的事情要做，因为我们不能将非 TVP 声明为READONLY. 例如以下失败：

create procedure [dbo].[test]
@a int readonly
as
    select @a

消息 346，级别 15，状态 1，过程测试
参数“@a”不能声明为 READONLY，因为它不是表值参数。

由于统计数据不存储在 TVP 上，阻止 DML 操作的原因是什么？
OUTPUT是否与出于某种原因不希望 TVP 成为参数有关？

Erik

Asked: 2015-10-09 20:22:27 +0800 CST

帮助找到没有谓词的连接

7

就像swasheck 提出的一个相关问题一样，我有一个历史上曾遇到过性能问题的查询。我正在查看 SSMS 上的查询计划并注意到Nested Loops (Inner Join)警告：

没有连接谓词

基于一些草率的研究（激发信心的Scary DBA和Brent Ozar），看起来这个警告告诉我我的查询中有一个隐藏的笛卡尔积。我检查了我的查询几次，但没有看到交叉连接。这是查询：

DECLARE @UserId INT; -- Stored procedure input
DECLARE @Now DATETIME2(7) = SYSUTCDATETIME();
;WITH AggregateStepData_CTE AS -- Considering converting this CTE into an indexed view
(
    SELECT 
        [UA].[UserId] -- FK to the UserId
        , [UA].[DeviceId] -- FK to the push device's DeviceId (int)
        , SUM(ISNULL([UA].[LatestSteps], 0)) AS [Steps]
    FROM [User].[UserStatus] [UA]
        INNER JOIN [User].[CurrentConnections] [M] ON 
           [M].[Monitored] = [UA].[UserId] AND [M].[Monitor] = @UserId
    WHERE
        [M].[ShareSteps] = 1 -- Only use step data if we are allowed to see.
        AND
        CAST([UA].[ReportedLocalTime] AS DATE) = 
          CAST(DATEADD(MINUTE, DATEPART(TZOFFSET, [UA].[ReportedLocalTime]), @Now) AS DATE)
          -- Aggregate the steps for today based on the device's time zone.         
    GROUP BY
        [UA].[UserId]
        , [UA].[DeviceId]
)
SELECT
    [UA].[UserId] -- FK to the UserId
    , [UA].[ReportedLocalTime]
    , CASE WHEN [M].[ShareLocation] = 1 THEN [UA].[Latitude] ELSE NULL END AS [Latitude]
    , CASE WHEN [M].[ShareLocation] = 1 THEN [UA].[Longitude] ELSE NULL END AS [Longitude]
    , CASE WHEN [M].[ShareLocation] = 1 THEN [UA].[LocationAccuracy] ELSE NULL END 
         AS [LocationAccuracy]
    , CASE WHEN [M].[ShareSteps] = 1 THEN ISNULL([SD].[Steps], 0) ELSE NULL END AS [Steps]
    , CASE WHEN [M].[ShareBattery] = 1 THEN [UA].[BatteryPercentage] ELSE NULL END 
         AS [BatteryPercentage]
    , CASE WHEN [M].[ShareBattery] = 1 THEN [UA].[IsDraining] ELSE NULL END 
         AS [IsDraining]
    , [PD].[DeviceName]
FROM [User].[LatestUserStatus] [UA]
    INNER JOIN [User].[CurrentConnections] [M] WITH (NOEXPAND) ON 
      [M].[Monitored] = [UA].[UserId] AND [M].[Monitor] = @UserId
    INNER JOIN [User].[PushDevice] [PD] ON [PD].[PushDeviceId] = [UA].[DeviceId]
    LEFT JOIN [AggregateStepData_CTE] [SD] ON 
      [M].[Monitored] = [SD].[UserId] AND [SD].[DeviceId] = [UA].[DeviceId]
ORDER BY        
    [UA].[UserId]
    , [UA].[ReportedLocalTime] DESC

可以在以下位置找到查询计划：https ://gist.github.com/anonymous/d6ac970b45eb75a88b99

还是我不应该像swasheck 问题中的结论那样害怕警告，毕竟估计的子树成本非常低，只有 0.05？

这个答案似乎也相关，这意味着这可能是 SQL Server 代表我进行的优化，因为它知道我可以删除连接。

这篇博文表明，嵌套循环没有谓词问题可能是由连接列上的 UDF 引起的。我没有在此查询中引用任何 UDF。

下面是CurrentConnections视图的定义：

CREATE VIEW [User].[CurrentConnections]
WITH SCHEMABINDING
AS 
    SELECT 
        [M].[Monitor] -- FK to the UserId
        , [M].[Monitored] -- FK to the UserId
        , [M].[MonitoringId]
        , [M].[ShareBattery]
        , [M].[ShareLocation]
        , [M].[ShareSteps]
        , [M].[ShowInSocialFeed]
        , [M].[Created] AS [RelationshipCreated]
        , [AT].[AlertThresholdId]
        , [AT].[EffectiveStartTime]
        , [AT].[EndTime]
        , [AT].[OverNightRedThreshold]
        , [AT].[SendBatteryAlerts]
        , [AT].[SendGeneralAlerts]
        , [AT].[StartTime]
        , [AT].[ThresholdInMinutes]
        , [AT].[Threshold]
        , [U_Monitored].[ProfilePhoto] AS [Monitored_ProfilePhoto]
        , [U_Monitored].[DisplayName] AS [Monitored_DisplayName]
        , [U_Monitored].[Fullname] AS [Monitored_FullName]
        , [U_Monitored].[PhoneNumber] AS [Monitored_PhoneNumber]
    FROM [User].[Monitoring] [M]
        INNER JOIN [User].[AlertThreshold] [AT] ON [AT].[MonitoringId] = [M].[MonitoringId]
        INNER JOIN [User].[User] [U_Monitored] ON [U_Monitored].[UserId] = [M].[Monitored]
    WHERE
        [M].[ArchivedOn] IS NULL
        AND
        [AT].[ArchivedOn] IS NULL

GO

CREATE UNIQUE CLUSTERED INDEX [IDX_User_CurrentConnections_Monitor_Monitored] ON 
   [User].[CurrentConnections]([Monitor], [Monitored]);
GO
CREATE NONCLUSTERED INDEX [IDX_User_CurrentConnections_Monitored] ON 
  [User].[CurrentConnections]([Monitored]) 
  INCLUDE ([Monitor], [ShareBattery], [ShareLocation], [ShareSteps]);

Erik

Asked: 2015-08-26 12:57:48 +0800 CST

基于时间戳的窗口偏移量

10

我正在编写一个查询，该查询将用于对社交提要的结果进行分页。这个概念是移动应用程序将请求 N 个项目，并提供我在@CutoffTime下面调用的开始日期时间。截止时间的目的是确定寻呼窗口何时开始。我们使用时间戳而不是行偏移量的原因是，即使添加了较新的社交内容，时间戳也能让我们在获取较旧的帖子时从一致的位置进行分页。

由于社交提要项目可以来自您自己或您的朋友，因此我使用UNION来合并这两个组的结果。最初我尝试了TheQuery_CTE没有的逻辑UNION，它很慢。

这就是我所做的（包括相关的表模式）：

    CREATE TABLE [Content].[Photo]
(
    [PhotoId] INT NOT NULL PRIMARY KEY IDENTITY (1, 1), 
    [Key] UNIQUEIDENTIFIER NOT NULL DEFAULT NEWID(),
    [FullResolutionUrl] NVARCHAR(255) NOT NULL, 
    [Description] NVARCHAR(255) NULL, 
    [Created] DATETIME2(2) NOT NULL DEFAULT SYSUTCDATETIME(),
);

CREATE TABLE [Content].[UserPhotoAssociation]
(
    [PhotoId] INT NOT NULL, 
    [UserId] INT NOT NULL, 
    [ShowInSocialFeed] BIT NOT NULL DEFAULT 0,

    CONSTRAINT [PK_UserPhotos] PRIMARY KEY ([PhotoId], [UserId]), 
    CONSTRAINT [FK_UserPhotos_User] FOREIGN KEY ([UserId]) 
        REFERENCES [User].[User]([UserId]), 
    CONSTRAINT [FK_UserPhotos_Photo] FOREIGN KEY ([PhotoId]) 
        REFERENCES [Content].[Photo]([PhotoId])
);

CREATE TABLE [Content].[FlaggedPhoto]
(
    [FlaggedPhotoId] INT NOT NULL PRIMARY KEY IDENTITY(1,1),
    [PhotoId] INT NOT NULL,
    [FlaggedBy] INT NOT NULL,
    [FlaggedOn] DATETIME2(0) NOT NULL DEFAULT SYSDATETIME(),
    [FlaggedStatus] INT NOT NULL DEFAULT 1,
    [ReviewedBy] INT NULL,
    [ReviewedAt] DATETIME2(0) NULL

    CONSTRAINT [FK_Photos_PhotoId_to_FlaggedPhotos_PhotoId] FOREIGN KEY ([PhotoId]) 
        REFERENCES [Content].[Photo]([PhotoId]),
    CONSTRAINT [FK_FlaggedPhotoStatus_FlaggedPhotoStatusId_to_FlaggedPhotos_FlaggedStatus] FOREIGN KEY ([FlaggedStatus]) 
        REFERENCES [Content].[FlaggedContentStatus]([FlaggedContentStatusId]),
    CONSTRAINT [FK_User_UserId_to_FlaggedPhotos_FlaggedBy] FOREIGN KEY ([FlaggedBy]) 
        REFERENCES [User].[User]([UserId]),
    CONSTRAINT [FK_User_UserId_to_FlaggedPhotos_ReviewedBy] FOREIGN KEY ([ReviewedBy]) 
        REFERENCES [User].[User]([UserId])
);


CREATE TABLE [User].[CurrentConnections]
(
    [MonitoringId] INT NOT NULL PRIMARY KEY IDENTITY,
    [Monitor] INT NOT NULL,
    [Monitored] INT NOT NULL,
    [ShowInSocialFeed] BIT NOT NULL DEFAULT 1,

    CONSTRAINT [FK_Monitoring_Monitor_to_User_UserId] FOREIGN KEY ([Monitor]) 
         REFERENCES [dbo].[User]([UserId]),
    CONSTRAINT [FK_Monitoring_Monitored_to_User_UserId] FOREIGN KEY ([Monitored]) 
         REFERENCES [dbo].[User]([UserId])
);

CREATE TABLE [Content].[PhotoLike]
(
    [PhotoLikeId] INT NOT NULL PRIMARY KEY IDENTITY,
    [PhotoId] INT NOT NULL,
    [UserId] INT NOT NULL,
    [Created] DATETIME2(2) NOT NULL DEFAULT SYSUTCDATETIME(),
    [Archived] DATETIME2(2) NULL,

    CONSTRAINT [FK_PhotoLike_PhotoId_to_Photo_PhotoId] FOREIGN KEY ([PhotoId]) 
         REFERENCES [Content].[Photo]([PhotoId]),
    CONSTRAINT [FK_PhotoLike_UserId_to_User_UserId] FOREIGN KEY ([UserId]) 
         REFERENCES [User].[User]([UserId])
);

CREATE TABLE [Content].[Comment]
(
    [CommentId] INT NOT NULL PRIMARY KEY IDENTITY,
    [PhotoId] INT NOT NULL,
    [UserId] INT NOT NULL,
    [Comment] NVARCHAR(255) NOT NULL,
    [Created] DATETIME2(2) NOT NULL DEFAULT SYSUTCDATETIME(),
    [CommentOrder] DATETIME2(2) NOT NULL DEFAULT SYSUTCDATETIME(),
    [Archived] DATETIME2(2) NULL,

    CONSTRAINT [FK_Comment_PhotoId_to_Photo_PhotoId] FOREIGN KEY ([PhotoId]) 
         REFERENCES [Content].[Photo]([PhotoId]),
    CONSTRAINT [FK_Comment_UserId_to_User_UserId] FOREIGN KEY ([UserId]) 
         REFERENCES [User].[User]([UserId])
);

/*

      End table schema

*/



DECLARE @UserId INT,
    @NumberOfItems INT,
    @CutoffTime DATETIME2(2) = NULL -- Stored Proc input params

-- Make the joins and grab the social data we need once since they are used in subsequent queries that aren't shown
DECLARE @SocialFeed TABLE ([Key] UNIQUEIDENTIFIER, [PhotoId] INT
            , [Description] NVARCHAR(255), [FullResolutionUrl] NVARCHAR(255)
            , [Created] DATETIME2(2), [CreatorId] INT, [LikeCount] INT
            , [CommentCount] INT, [UserLiked] BIT);
-- Offset might be different for each group
DECLARE @OffsetMine INT = 0, @OffsetTheirs INT = 0;

IF @CutoffTime IS NOT NULL
    BEGIN
        -- Get the offsets
        ;WITH [GetCounts_CTE] AS
        (
            SELECT
                [P].[PhotoId] -- INT
                , 1 AS [MyPhotos]
            FROM [Content].[Photo] [P]
                INNER JOIN [Content].[UserPhotoAssociation] [UPA] ON 
                    [UPA].[PhotoId] = [P].[PhotoId] 
                    AND 
                    [UPA].[ShowInSocialFeed] = 1
                LEFT JOIN [Content].[FlaggedPhoto] [FP] ON 
                    [FP].[PhotoId] = [P].[PhotoId] 
                    AND 
                    [FP].[FlaggedStatus] = 3 -- Flagged photos that are confirmed apply to everyone
            WHERE
                [FP].[FlaggedPhotoId] IS NULL -- Filter out flagged photos
                AND
                [UPA].[UserId] = @UserId -- Show the requesting user
                AND
                [P].[Created] >= @CutoffTime -- Get the newer items
            UNION
            SELECT
                [P].[PhotoId] -- INT
                , 0 AS [MyPhotos]
            FROM [Content].[Photo] [P]
                INNER JOIN [Content].[UserPhotoAssociation] [UPA] ON 
                    [UPA].[PhotoId] = [P].[PhotoId] 
                    AND 
                    [UPA].[ShowInSocialFeed] = 1
                INNER JOIN [User].[CurrentConnections] [M] ON 
                    [M].[Monitored] = [UPA].[UserId] 
                    AND 
                    [M].[Monitor] = @UserId AND [M].[ShowInSocialFeed] = 1 -- this join isn't present above  
                LEFT JOIN [Content].[FlaggedPhoto] [FP] ON 
                    [FP].[PhotoId] = [P].[PhotoId] 
                    AND 
                    (
                        [FP].[FlaggedStatus] = 3 
                        OR 
                        ([FP].[FlaggedBy] = @UserId AND [FP].[FlaggedStatus] = 1)
                    ) -- Flagged photos that are confirmed apply to everyone, pending flags apply to the user
            WHERE
                [FP].[FlaggedPhotoId] IS NULL -- Filter out flagged photos
                AND
                [P].[Created] >= @CutoffTime -- Get the newer items
        )
        SELECT
            @OffsetMine = SUM(CASE WHEN [MyPhotos] = 1 THEN 1 ELSE 0 END)
            , @OffsetTheirs = SUM(CASE WHEN [MyPhotos] = 0 THEN 1 ELSE 0 END)
        FROM [GetCounts_CTE]
    END

-- Prevent absence of social data from throwing an error below.
SET @OffsetMine = ISNULL(@OffsetMine, 0); 
SET @OffsetTheirs = ISNULL(@OffsetTheirs, 0);

-- Actually select the data I want
;WITH TheQuery_CTE AS
(
    SELECT
        [P].[Key]
        , [P].[PhotoId]
        , [P].[Description]
        , [P].[FullResolutionUrl]
        , [P].[Created]
        , [UPA].[UserId]
        , COUNT(DISTINCT [PL].[PhotoLikeId]) AS [LikeCount] -- Count distinct used due to common join key
        , COUNT(DISTINCT [C].[CommentId]) AS [CommentCount]
        , CAST(ISNULL(MAX(CASE WHEN [PL].[UserId] = @UserId THEN 1 END), 0) AS BIT) AS [UserLiked]
    FROM [Content].[Photo] [P]
        INNER JOIN [Content].[UserPhotoAssociation] [UPA] ON 
            [UPA].[PhotoId] = [P].[PhotoId] 
            AND 
            [UPA].[ShowInSocialFeed] = 1
        LEFT JOIN [Content].[PhotoLike] [PL] ON 
            [PL].[PhotoId] = [P].[PhotoId] 
            AND 
            [PL].[Archived] IS NULL
        LEFT JOIN [Content].[Comment] [C] ON 
            [C].[PhotoId] = [P].[PhotoId] 
            AND 
            [C].[Archived] IS NULL
        LEFT JOIN [Content].[FlaggedPhoto] [FP] ON 
            [FP].[PhotoId] = [P].[PhotoId] 
            AND 
            [FP].[FlaggedStatus] = 3 -- Flagged photos that are confirmed apply to everyone
    WHERE
        [FP].[FlaggedPhotoId] IS NULL -- Filter out flagged photos
        AND
        [UPA].[UserId] = @UserId -- Show the requesting user
    GROUP BY
        [P].[Key]
        , [P].[PhotoId]
        , [P].[Description]
        , [P].[FullResolutionUrl]
        , [P].[Created]
        , [UPA].[UserId]
    ORDER BY  
        [P].[Created] DESC
        , [P].[Key]  -- Ensure consistent order in case of duplicate timestamps
        OFFSET @OffsetMine ROWS FETCH NEXT @NumberOfItems ROWS ONLY
    UNION
    SELECT
        [P].[Key]
        , [P].[PhotoId]
        , [P].[Description]
        , [P].[FullResolutionUrl]
        , [P].[Created]
        , [UPA].[UserId]
        , COUNT(DISTINCT [PL].[PhotoLikeId]) AS [LikeCount]
        , COUNT(DISTINCT [C].[CommentId]) AS [CommentCount]
        , CAST(ISNULL(MAX(CASE WHEN [PL].[UserId] = @UserId THEN 1 END), 0) AS BIT) AS [UserLiked]
    FROM [Content].[Photo] [P]
        INNER JOIN [Content].[UserPhotoAssociation] [UPA] ON 
            [UPA].[PhotoId] = [P].[PhotoId] 
            AND 
            [UPA].[ShowInSocialFeed] = 1
        INNER JOIN [User].[CurrentConnections] [M] ON 
            [M].[Monitored] = [UPA].[UserId] 
            AND 
            [M].[Monitor] = @UserId AND [M].[ShowInSocialFeed] = 1
        LEFT JOIN [Content].[PhotoLike] [PL] ON 
            [PL].[PhotoId] = [P].[PhotoId] 
            AND 
            [PL].[Archived] IS NULL
        LEFT JOIN [Content].[Comment] [C] ON 
            [C].[PhotoId] = [P].[PhotoId] 
            AND 
            [C].[Archived] IS NULL
        LEFT JOIN [Content].[FlaggedPhoto] [FP] ON 
            [FP].[PhotoId] = [P].[PhotoId] 
            AND 
            (
                [FP].[FlaggedStatus] = 3 
                OR 
                ([FP].[FlaggedBy] = @UserId AND [FP].[FlaggedStatus] = 1)
            ) -- Flagged photos that are confirmed apply to everyone, pending flags apply to the user
    WHERE
        [FP].[FlaggedPhotoId] IS NULL -- Filter out flagged photos
    GROUP BY
        [P].[Key]
        , [P].[PhotoId]
        , [P].[Description]
        , [P].[FullResolutionUrl]
        , [P].[Created]
        , [UPA].[UserId]
    ORDER BY  
        [P].[Created] DESC
        , [P].[Key]  -- Ensure consistant order in case of duplicate timestamps
        OFFSET @OffsetTheirs ROWS FETCH NEXT @NumberOfItems ROWS ONLY
)
INSERT INTO @SocialFeed ([Key], [PhotoId], [Description], [FullResolutionUrl]
            , [Created], [CreatorId], [LikeCount], [CommentCount], [UserLiked])
SELECT TOP (@NumberOfItems)
    [Key]
    , [PhotoId]
    , [Description]
    , [FullResolutionUrl]
    , [Created]
    , [UserId]
    , [LikeCount]
    , [CommentCount]
    , [UserLiked]
FROM [TheQuery_CTE]
ORDER BY  -- Order here so the top works properly
    [Created] DESC
    , [Key]  -- Ensure consistent order in case of duplicate timestamps

-- Output the social feed
SELECT
    [P].[Key]
    , [P].[PhotoId]
    , [P].[Description] AS [PhotoDescription]
    , [P].[FullResolutionUrl]
    , [P].[Created] AS [Posted]
    , [P].[CreatorId]
    , [LikeCount]
    , [CommentCount]
    , [UserLiked]
FROM @Photos [P]

-- Select other data needed to build the object tree in the application layer

我意识到我可以摆脱UNIONin theGetCounts_CTE但我认为它不会真正解决我在下面看到的任何问题。

我看到一些潜在的问题：

这是很多重复的逻辑，所以我可能让自己的生活更加艰难。
如果在计算计数和选择数据之间发生插入，我将关闭。我不认为这会经常发生，但它会导致奇怪/难以调试的错误。
通过上述设置，人们会发现所有更聪明/更有经验的问题。

编写此查询的最佳方式是什么？奖励积分解决方案使我的生活更简单。

编辑：

我不想选择所有数据并让客户端懒惰地显示项目，因为我不想通过强迫人们下载他们永远看不到的项目来滥用人们的数据计划。诚然，在宏伟的计划中，数据可能不会那么大，但一分钱一分货……

编辑 2：

我强烈怀疑这不是最佳解决方案，但这是迄今为止我想到的最好的解决方案。

将我的UNION查询移动到VIEW像Greg建议的那样可以很好地隐藏该逻辑并在我的存储过程中提供更简洁的查询。该视图还抽象掉了联合的丑陋/复杂性，这很好，因为我在我的选择中使用了它两次。这是视图的代码：

CREATE VIEW [Social].[EverFeed]
    AS 
SELECT
    [P].[Key]
    , [P].[PhotoId]
    , [P].[Description]
    , [P].[FullResolutionUrl]
    , [P].[Created]
    , [UPA].[UserId]
    , COUNT(DISTINCT [PL].[PhotoLikeId]) AS [LikeCount] -- Distinct due to common join key
    , COUNT(DISTINCT [C].[CommentId]) AS [CommentCount]
    , CAST(ISNULL(
        MAX(CASE WHEN [PL].[UserId] = [UPA].[UserId] THEN 1 END), 0) AS BIT) AS [UserLiked]
    , NULL AS [Monitor]
FROM [Content].[Photo] [P]
    INNER JOIN [Content].[UserPhotoAssociation] [UPA] ON 
        [UPA].[PhotoId] = [P].[PhotoId] 
        AND 
        [UPA].[ShowInSocialFeed] = 1
    LEFT JOIN [Content].[PhotoLike] [PL] ON 
        [PL].[PhotoId] = [P].[PhotoId] 
        AND 
        [PL].[Archived] IS NULL
    LEFT JOIN [Content].[Comment] [C] ON 
        [C].[PhotoId] = [P].[PhotoId] 
        AND 
        [C].[Archived] IS NULL
    LEFT JOIN [Content].[FlaggedPhoto] [FP] ON 
        [FP].[PhotoId] = [P].[PhotoId] 
        AND 
        [FP].[FlaggedStatus] = 3 -- Flagged photos that are confirmed apply to everyone
WHERE
    [FP].[FlaggedPhotoId] IS NULL -- Filter out flagged photos
GROUP BY
    [P].[Key]
    , [P].[PhotoId]
    , [P].[Description]
    , [P].[FullResolutionUrl]
    , [P].[Created]
    , [UPA].[UserId]
UNION
SELECT
    [P].[Key]
    , [P].[PhotoId]
    , [P].[Description]
    , [P].[FullResolutionUrl]
    , [P].[Created]
    , [UPA].[UserId]
    , COUNT(DISTINCT [PL].[PhotoLikeId]) AS [LikeCount]
    , COUNT(DISTINCT [C].[CommentId]) AS [CommentCount]
    , CAST(ISNULL(
        MAX(CASE WHEN [PL].[UserId] = [M].[Monitor] THEN 1 END), 0) AS BIT) AS [UserLiked]
    , [M].[Monitor]
FROM [Content].[Photo] [P]
    INNER JOIN [Content].[UserPhotoAssociation] [UPA] ON 
        [UPA].[PhotoId] = [P].[PhotoId] 
        AND 
        [UPA].[ShowInSocialFeed] = 1
    INNER JOIN [User].[CurrentConnections] [M] ON 
        [M].[Monitored] = [UPA].[UserId] 
        AND 
        [M].[ShowInSocialFeed] = 1
    LEFT JOIN [Content].[PhotoLike] [PL] ON 
        [PL].[PhotoId] = [P].[PhotoId] 
        AND 
        [PL].[Archived] IS NULL
    LEFT JOIN [Content].[Comment] [C] ON 
        [C].[PhotoId] = [P].[PhotoId] 
        AND 
        [C].[Archived] IS NULL
    LEFT JOIN [Content].[FlaggedPhoto] [FP] ON 
        [FP].[PhotoId] = [P].[PhotoId] 
        AND 
        (
            [FP].[FlaggedStatus] = 3 
            OR 
            ([FP].[FlaggedBy] = [M].[Monitor] AND [FP].[FlaggedStatus] = 1)
        ) -- Flagged photos that are confirmed (3) apply to everyone
          -- , pending flags (1) apply to the user
WHERE
    [FP].[FlaggedPhotoId] IS NULL -- Filter out flagged photos
GROUP BY
    [P].[Key]
    , [P].[PhotoId]
    , [P].[Description]
    , [P].[FullResolutionUrl]
    , [P].[Created]
    , [UPA].[UserId]
    , [M].[Monitor]

Using that view I shortened my query to the following. Note I'm setting the OFFSET with a subquery.

DECLARE @UserId INT, @NumberOfItems INT, @CutoffTime DATETIME2(2);

SELECT
    [Key]
    , [PhotoId]
    , [Description]
    , [FullResolutionUrl]
    , [Created]
    , [UserId]
    , [LikeCount]
    , [CommentCount]
    , [UserLiked]
FROM  [Social].[EverFeed] [EF]
WHERE
    (
        ([EF].[UserId] = @UserId AND [EF].[Monitor] IS NULL)
        OR 
        [EF].[Monitor] = @UserId
    )
ORDER BY  -- Order here so the top works properly
    [Created] DESC
    , [Key]  -- Ensure consistant order in case of duplicate timestamps
    OFFSET CASE WHEN @CutoffTime IS NULL THEN 0 ELSE        
            (
                SELECT
                    COUNT([PhotoId])
                FROM [Social].[EverFeed] [EF]
                WHERE
                    (
                        ([EF].[UserId] = @UserId AND [EF].[Monitor] IS NULL)
                        OR 
                        [EF].[Monitor] = @UserId
                    )
                    AND
                    [EF].[Created] >= @CutoffTime -- Get the newer items
            ) END 
    ROWS FETCH NEXT @NumberOfItems ROWS ONLY

The view nicely separates the complexity of the UNION from the filtering. I think the subquery in the OFFSET clause will prevent concurrency issues that I was worried about by making the whole query atomic.

One problem I just found while typing this is: in the code above if two photos with the same creation date are on different "pages" then the photos on the subsequent pages will be filtered out. Consider the following data:

PhotoId | Created | ...
------------------------
   1    | 2015-08-26 01:00.00
   2    | 2015-08-26 01:00.00
   3    | 2015-08-26 01:00.00

With a page size of 1 on the initial page, PhotoId 1 will be returned. With the same page size on the second page no results will be returned. I think in order to resolve this I'm going to have to add the Key Guid as a parameter....

Erik

Asked: 2015-08-05 09:31:31 +0800 CST

如何让 Brent Ozar 的 sp_BlitzIndex 在 Azure 上运行？

14

我从 Brent Ozar 的网站下载了 SQL Server 急救包。当我以 Azure 数据库服务器级别管理员身份登录时，尝试通过 Microsoft Sql Server Management Studio 对我的主数据库运行sp_BlitzIndex脚本时，出现以下错误：

消息 262，级别 14，状态 18，过程 sp_BlitzIndex，第 18 行数据库“主”中的创建过程权限被拒绝。

我在要测试的数据库实例上成功创建了该过程。当我执行该过程时，我收到一条错误消息：

消息 50000，级别 16，状态 1，第 1265 行无效的对象名称“mydatabase.sys.partitions”。

接下来我想聪明点，直接针对master数据库运行存储过程代码，不创建存储过程，得到如下错误：

消息 50000，级别 15，状态 1，第 1267 行对“mydatabase.sys.indexes”中的数据库和/或服务器名称的引用在此版本的 SQL Server 中不受支持。

我没有足够的信心开始玩弄约 2700 行索引启发式逻辑的内部工作原理。有没有一种快速、简单的方法可以让这个存储过程在 Azure SQL 数据库上很好地工作，或者我应该在别处寻找索引分析工具/存储过程？

消除内部查询死锁，我可以避免限制并行性吗？

像这样拼接一个字符串会让我面临 SQL 注入吗？

我应该警惕 ON DUPLICATE KEY UPDATE 吗？

与交易计数相关的规则

为什么 TVP 必须是 READONLY，其他类型的参数为什么不能是 READONLY

帮助找到没有谓词的连接

基于时间戳的窗口偏移量

我强烈怀疑这不是最佳解决方案，但这是迄今为止我想到的最好的解决方案。

如何让 Brent Ozar 的 sp_BlitzIndex 在 Azure 上运行？

连接到 PostgreSQL 服务器：致命：主机没有 pg_hba.conf 条目

如何让sqlplus的输出出现在一行中？

选择具有最大日期或最晚日期的日期

如何列出 PostgreSQL 中的所有模式？

列出指定表的所有列

如何在不修改我自己的 tnsnames.ora 的情况下使用 sqlplus 连接到位于另一台主机上的 Oracle 数据库

你如何mysqldump特定的表？

使用 psql 列出数据库权限

如何从 PostgreSQL 中的选择查询中将值插入表中？

如何使用 psql 列出所有数据库和表？

Erik's questions

我强烈怀疑这不是最佳解决方案，但这是迄今为止我想到的最好的解决方案。