我們在操作表的時候難免會遇到誤刪除，或者刪掉的資料還想恢復的情況。也許細心的朋友會用begin tran rollback/commit 這種事務來避免出現失誤，但這並不是最保險的。如果提交了事物發現刪錯了或者忘記提交從而導致表被鎖，這些問題總是不可避免的。廢話不多說了，下面直接進入正題，通過觸發器記錄刪除日誌，避免誤刪除帶來的尷尬。

下面這段sql粘過去直接執行，建立一個儲存過程：

CREATE PROCEDURE [dbo].[SP_DELETE_LOG]
    @TABLENAME VARCHAR(50)
AS
BEGIN
	SET NOCOUNT ON;
    IF NOT EXISTS(SELECT * FROM sys.tables WHERE NAME = @TABLENAME AND TYPE = 'U' )
	BEGIN
		PRINT'ERROR：not exist table '
 
[email protected]
		RETURN
	END
	IF (@TABLENAME LIKE'BACKUP_%' OR @TABLENAME='UPDATE_LOG' )
	BEGIN
		--PRINT'ERROR：not exist table '[email protected]
		RETURN
	END
	--================================判斷是否存在 UPDATE_LOG 表============================
	IF NOT EXISTS(SELECT * FROM sys.tables WHERE NAME = 'UPDATE_LOG' AND TYPE = 'U')
		CREATE TABLE UPDATE_LOG
		(
			UpdateGUID VARCHAR(36),
			UpdateTime DATETIME,
			TableName varchar(20),
			UpdateType varchar(6),
			RollBackSQL varchar(1000)
		)
	--=================================判斷是否存在 BACKUP_ 表================================
	IF NOT EXISTS(SELECT * FROM sys.tables WHERE NAME = 'BACKUP_'
 
[email protected] AND TYPE = 'U')
	BEGIN
		--DECLARE @SQL VARCHAR(500)
		--SET @SQL='SELECT TOP 1 NEWID() AS [UpdateGUID],* INTO BACKUP_'[email protected]+' FROM '+ @TABLENAME+'
		--		  DELETE FROM BACKUP_'[email protected]
		--SELECT @SQL
		--EXEC(@SQL)
		DECLARE test_Cursor CURSOR FOR
		SELECT COLUMN_NAME,DATA_TYPE,CHARACTER_MAXIMUM_LENGTH FROM INFORMATION_SCHEMA.columns 
		WHERE 
 
[email protected]
		OPEN test_Cursor
		DECLARE @SQLTB NVARCHAR(MAX)=''
		DECLARE @COLUMN_NAME NVARCHAR(50),@DATA_TYPE VARCHAR(20),@CHARACTER_MAXIMUM_LENGTH INT
		FETCH NEXT FROM test_Cursor INTO @COLUMN_NAME,@DATA_TYPE,@CHARACTER_MAXIMUM_LENGTH
		WHILE @@FETCH_STATUS=0
		BEGIN
			SET @[email protected]+'['[email protected]_NAME+'] '[email protected]_TYPE+CASE ISNULL(@CHARACTER_MAXIMUM_LENGTH,0) WHEN 0 THEN '' WHEN -1 THEN '(MAX)' ELSE'('+CAST(@CHARACTER_MAXIMUM_LENGTH AS VARCHAR(10))+')' END+','
			FETCH NEXT FROM test_Cursor INTO @COLUMN_NAME,@DATA_TYPE,@CHARACTER_MAXIMUM_LENGTH
		END
		SET @SQLTB='CREATE TABLE BACKUP_'[email protected]+' (UpdateGUID varchar(36),'+SUBSTRING(@SQLTB,1,LEN(@SQLTB)-1)+')'
		EXEC (@SQLTB)
		CLOSE test_Cursor 
		DEALLOCATE test_Cursor
	END
	--======================================判斷是否存在 DELETE 觸發器=========================
	IF NOT EXISTS(SELECT * FROM sys.objects WHERE NAME = 'tg_'[email protected]+'_Delete' AND TYPE = 'TR')
	BEGIN
		DECLARE @SQLTR NVARCHAR(MAX)
		SET @SQLTR='
			CREATE TRIGGER tg_'[email protected]+'_Delete
				ON  '[email protected]+'
				AFTER delete
			AS 
			BEGIN	
				SET NOCOUNT ON;
				--==============================獲取GUID==========================================
				DECLARE @NEWID VARCHAR(36)=NEWID()

				--==============================將刪掉的資料插入備份表============================
				INSERT INTO [dbo].[BACKUP_'[email protected]+']
				SELECT @NEWID,* FROM deleted

				--==============================記錄日誌和回滾操作的SQL===========================
				--*********************生成列名**********************
				DECLARE @COLUMN NVARCHAR(MAX)=''''
				SELECT @COLUMN+='',[''+COLUMN_NAME+'']'' FROM INFORMATION_SCHEMA.columns
				WHERE TABLE_NAME='''[email protected]+''' 
				AND COLUMNPROPERTY(OBJECT_ID('''[email protected]+'''),COLUMN_NAME,''IsIdentity'')<>1 --非自增欄位
				SET @COLUMN=SUBSTRING(@COLUMN,2,LEN(@COLUMN))

				INSERT INTO [dbo].[UPDATE_LOG]
				SELECT @NEWID,GETDATE(),'''[email protected]+''',''DELETE'',''INSERT INTO '[email protected]+' SELECT ''[email protected]+'' FROM BACKUP_'[email protected]+' WHERE UPDATEGUID=''''''[email protected]+''''''''

			END
			'
		EXEC(@SQLTR)
	END
END

接著我們新建一張測試表，並且隨便往表中插入兩組資料：

 Create table test 
 (
	id int,
	name varchar(10),
	msg varchar(10)
 )
 Insert into test
 Select 1,'aa','hahah'
 Union all 
 Select 2,'bb','heihei'

下面執行這個SP,在給test表添加回滾日誌：

 EXEC SP_DELETE_LOG 'test'

細心的你不難發現，這時候資料庫裡面應該會多出兩張表： 然後我們刪掉一條資料：

DELETE FROM test WHERE id=1

再檢視那兩張表： 沒錯，這時候日誌表裡有資料了，然後我們把 UPDATE_LOG 表中的 RollBackSQ L這一列對應的值copy出來執行一下：

 INSERT INTO test SELECT [id],[name],[msg] FROM BACKUP_test WHERE UPDATEGUID='B0CBBC4F-3432-4D4F-9E17-F17209BF6745'

別copy我上面這段sql，因為GUID肯定是不一樣的！ 然而，資料恢復了：
最後，delete日誌的介紹就結束了，唯一的不滿足的是隻能作用在Delete 操作，其實UPDATE 操作也同樣需要這樣的回滾日誌。 今天就到這裡結束了，下一篇我會介紹關於UPDATE的回滾日誌的建立。Bye Bye~~~