T-SQL 觸發器 - 如果滿足條件，則刪除更新的記錄

Question

我需要為 Microsoft SQL Server 2017 Enterprise 數據庫中的所有表編寫一個觸發器，如果列is_deleted = 1和change_user = 'purge' ，則刪除更新的行而不是更新它。

這需要是一個動態觸發器，以便每個表觸發器不需要顯式定義表。 該環境有超過 1200 個表。

但是，我只希望刪除語句刪除插入的記錄，而不是 go 整個表，我相信下面的觸發器會這樣做。 該環境具有包含 100+ 百萬條記錄的表，並且將貫穿整個表的刪除語句會產生大量開銷，並且可能無法跟上每小時 200 萬個事務。

CREATE OR ALTER TRIGGER [PurgeDelete]
ON [TriggerTest]
AFTER UPDATE
AS
    DECLARE @SQL NVARCHAR(1000)
    DECLARE @SchemaName NVARCHAR(100) = (SELECT OBJECT_SCHEMA_NAME( parent_id ) FROM sys.triggers WHERE object_id = @@PROCID)
    DECLARE @TableName NVARCHAR(100) = (SELECT OBJECT_NAME( parent_id ) tableName FROM sys.triggers WHERE object_id = @@PROCID)

    IF (ROWCOUNT_BIG() = 0)
        RETURN;

    IF EXISTS (SELECT 1
               FROM Inserted AS i
               WHERE is_deleted = 1
               AND change_user = 'purge')
    BEGIN
        SET @SQL = 'DELETE FROM ' + @SchemaName + '.' + @TableName + ' WHERE is_deleted = 1 AND change_user = ''purge'''
        EXECUTE sp_executesql @SQL
    END
GO

UPDATE [TriggerTest] 
SET [Description] = 'Test 1a', [is_deleted] = 1, [change_user] = 'Purge' 
WHERE [TriggerTestId] = 1

SELECT * FROM [TriggerTest];
GO

Answer 1

您的觸發器代碼需要訪問inserted和deleted的表。 您無法使用動態 SQL 執行此操作，因為您在不同的 scope 中。

在任何情況下，如果您想要一個動態觸發器，我會建議改為制作一個腳本來動態生成觸發器，但一旦生成觸發器將是 static。

所以基本模板是這樣的：

CREATE OR ALTER TRIGGER TriggerTest_PurgeDelete
ON dbo.TriggerTest
AFTER UPDATE
AS

    SET NOCOUNT ON;

    IF EXISTS (SELECT 1
               FROM inserted AS i
               WHERE is_deleted = 1
               AND change_user = 'purge')
    BEGIN
        DELETE FROM t
        FROM dbo.TriggerTest t
        JOIN inserted i ON i.YourPrimaryKey = t.YourPrimaryKey
        WHERE i.is_deleted = 1
          AND i.change_user = 'purge';
    END;

現在你只需要一個可以動態生成的腳本

-- user provided table/schema name here
DECLARE @schema sysname = 'dbo';
DECLARE @table sysname = 'TriggerTest';


DECLARE @quoted nvarchar(1000) = QUOTENAME(@schema) + '.' + QUOTENAME(@table);

DECLARE @primaryKeys nvarchar(max);

SELECT @primaryKeys = STRING_AGG(
  'i.' + QUOTENAME(c.name) + ' = t.' + QUOTENAME(c.name),
  ' AND '
  )
FROM sys.tables t
JOIN sys.schemas s ON s.schema_id = t.schema_id
JOIN sys.indexes i ON t.object_id = i.object_id
    AND i.is_primary_key = 1
JOIN sys.index_columns ic ON ic.object_id = i.object_id
    AND ic.index_id = i.index_id
JOIN sys.columns c ON c.object_id = t.object_id
    AND c.column_id = i.column_id
WHERE s.name = @schema
  AND t.name = @table
  AND pk.type = 'P';


DECLARE @sql nvarchar(max) = '
CREATE OR ALTER TRIGGER ' + QUOTENAME(@schema + '_' + @table + '_PD') + '
ON ' + @quoted + '
AFTER UPDATE
AS

    SET NOCOUNT ON;

    IF EXISTS (SELECT 1
               FROM inserted AS i
               WHERE is_deleted = 1
               AND change_user = 'purge')
    BEGIN
        DELETE FROM t
        FROM ' + @quoted + ' t
        JOIN inserted i ON ' + @primaryKeys + '
        WHERE i.is_deleted = 1
          AND i.change_user = ''purge'';
    END;
';

EXEC sp_executesql @sql;

理論上，您可以使用INSTEAD OF觸發器，如果刪除經常發生，這可能會更有效，但它也更難以管理，因為每次ALTER表中的任何列都需要更新。