Sql 而不是为多个表插入触发器

对于日志记录系统，我希望具有以下数据库架构：

CREATE TABLE [dbo].[Categories] (
    [Id]       INT            IDENTITY (1, 1) NOT NULL,
    [App]      NVARCHAR (30)  NULL,
    [Source]   NVARCHAR (30)  NULL,
    [LogLevel] NVARCHAR (5)   NULL,
    [Logger]   NVARCHAR (120) NULL,
    CONSTRAINT [PK_Categories] PRIMARY KEY NONCLUSTERED ([Id] ASC),
    CONSTRAINT [UK_Categories] UNIQUE NONCLUSTERED ([App] ASC, [Source] ASC, [LogLevel] ASC, [Logger] ASC)
);

CREATE TABLE [dbo].[Occurences] (
    [PointInTime] BIGINT NOT NULL,
    [CategoryId]  INT    NOT NULL,
    [Noise]       INT    NOT NULL,
    CONSTRAINT [PK_Occurences] PRIMARY KEY CLUSTERED ([PointInTime] ASC, [CategoryId] ASC, [Noise] ASC),
    CONSTRAINT [FK_Category] FOREIGN KEY ([CategoryId]) REFERENCES [Categories] ([Id])
);

设计目标是允许大量的日志数据，因为更昂贵的字符串被分解到一个单独的表中

从语义上讲，这两个表构成了此视图定义的单个逻辑表：

CREATE VIEW [dbo].[HistoricLogEntries]
    AS SELECT o.PointInTime, o.Noise, c.App, c.[Source], c.LogLevel, c.Logger
    FROM Occurences o
    JOIN Categories c ON o.CategoryId = c.Id;

现在，我想在视图上定义一个insert触发器，而不是insert触发器，这就是我的麻烦开始的地方。我有以下尝试：

CREATE TRIGGER InsteadTrigger on [dbo].[HistoricLogEntries]
INSTEAD OF INSERT
AS
BEGIN
    INSERT INTO Categories
    SELECT i.App, i.[Source], i.LogLevel, i.Logger
    FROM INSERTED i;

    INSERT INTO Occurences
    SELECT i.PointInTime, i.Noise, c.Id AS CategoryId
    FROM INSERTED i
    JOIN Categories c ON i.App = c.App AND i.[Source] = c.[Source] AND i.LogLevel = c.LogLevel AND i.Logger = c.Logger;
END

第一个明显的问题是，第一次插入没有检查元组是否已经在数据库中。我知道在单值插入的情况下如何执行该操作，但这里我必须考虑多行插入

另一件我无法解释的事情是，如果第一次插入成功，触发器甚至不起作用。我得到一个外键冲突-好像第一次插入实际上没有插入任何东西

---

我认为这应该是一个常见的设置，所以可能有人有一些类似的示例代码？

对于SQL2008+我会使用MERGE语句插入新的类别：

MERGE dbo.Categories WITH (HOLDLOCK) AS c
USING INSERTED AS i ON i.App = c.App
AND i.[Source] = c.[Source]
AND i.LogLevel = c.LogLevel
AND i.Logger = c.Logger
WHEN NOT MATCHED BY TARGET THEN
    INSERT (App, [Source], LogLevel, Logger)
    VALUES (i.App, i.[Source], i.LogLevel, i.Logger);

我使用了

HOLDLOCK

表格提示：

[…]以防止并发会话插入具有相同 密钥，必须获取不兼容的锁以确保只有一个会话 可以读取密钥（我的注释：在本例中为UK_Categories unique index），并且该锁必须一直保持到交易结束 完成。[…]

为防止FK错误，请执行以下操作：

The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Category". The conflict occurred in database "Test", table "dbo.Categories", column 'Id'.

我会在second

INSERT

中添加每个列的名称，因此：

INSERT INTO Occurences (PointInTime, Noise, CategoryId)
SELECT i.PointInTime, i.Noise, c.Id AS CategoryId
FROM INSERTED i
JOIN Categories c ON i.App = c.App

这些FK错误的原因是列顺序不一致：

1） CREATE TABLE中列的顺序为

   [PointInTime] BIGINT NOT NULL,
    [CategoryId]  INT    NOT NULL,
    [Noise]       INT    NOT NULL,

但是

2） 在第二次插入中，列的顺序不同（请参见类别ID vs Noise）：

这是我的解决方案：

ALTER TRIGGER InsteadTrigger on [dbo].[HistoricLogEntries]
INSTEAD OF INSERT
AS
BEGIN       
    MERGE dbo.Categories WITH (HOLDLOCK) AS c
    USING INSERTED AS i ON i.App = c.App
    WHEN NOT MATCHED BY TARGET THEN
        INSERT (App)
        VALUES (i.App);

    INSERT INTO Occurences (PointInTime, Noise, CategoryId)
    SELECT i.PointInTime, i.Noise, c.Id AS CategoryId
    FROM INSERTED i
    JOIN Categories c ON i.App = c.App
END
GO

---

这真的很全面，而且在我发布问题后很快。非常感谢你！

ALTER TRIGGER InsteadTrigger on [dbo].[HistoricLogEntries]
INSTEAD OF INSERT
AS
BEGIN       
    MERGE dbo.Categories WITH (HOLDLOCK) AS c
    USING INSERTED AS i ON i.App = c.App
    WHEN NOT MATCHED BY TARGET THEN
        INSERT (App)
        VALUES (i.App);

    INSERT INTO Occurences (PointInTime, Noise, CategoryId)
    SELECT i.PointInTime, i.Noise, c.Id AS CategoryId
    FROM INSERTED i
    JOIN Categories c ON i.App = c.App
END
GO