SQL开发知识：SQL Server 添加Delete操作回滚日志方式
我们在操作表的时候难免会遇到误删除，或者删掉的数据还想恢复的情况。
也许细心的朋友会用begin tran rollback/commit 这种事务来避免出现失误，但这并不是最保险的。
如果提交了事物发现删错了或者忘记提交从而导致表被锁，这些问题总是不可避免的。
废话不多说了，下面直接进入正题，通过触发器记录删除日志，避免误删除带来的尴尬。
下面这段sql粘过去直接运行，建立一个存储过程：
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 ‘+@TABLENAME
RETURN
END
IF (@TABLENAME LIKE’BACKUP_%’ OR @TABLENAME=’UPDATE_LOG’ )
BEGIN
–PRINT’ERROR：not exist table ‘+@TABLENAME
RETURN
END
–================================判断是否存在 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)
)
–=================================判断是否存在 BACKUP_ 表================================
IF NOT EXISTS(SELECT * FROM sys.tables WHERE NAME = ‘BACKUP_’+@TABLENAME AND TYPE = ‘U’)
BEGIN
–DECLARE @SQL VARCHAR(500)
–SET @SQL=’SELECT TOP 1 NEWID() AS [UpdateGUID],* INTO BACKUP_’+@TABLENAME+’ FROM ‘+ @TABLENAME+’
— DELETE FROM BACKUP_’+@TABLENAME
–SELECT @SQL
–EXEC(@SQL)
DECLARE test_Cursor CURSOR FOR
SELECT COLUMN_NAME,DATA_TYPE,CHARACTER_MAXIMUM_LENGTH FROM INFORMATION_SCHEMA.columns
WHERE TABLE_NAME=@TABLENAME
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 @SQLTB=@SQLTB+'[‘+@COLUMN_NAME+’] ‘+@DATA_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_’+@TABLENAME+’ (UpdateGUID varchar(36),’+SUBSTRING(@SQLTB,1,LEN(@SQLTB)-1)+’)’
EXEC (@SQLTB)
CLOSE test_Cursor
DEALLOCATE test_Cursor
END
–======================================判断是否存在 DELETE 触发器=========================
IF NOT EXISTS(SELECT * FROM sys.objects WHERE NAME = ‘tg_’+@TABLENAME+’_Delete’ AND TYPE = ‘TR’)
BEGIN
DECLARE @SQLTR NVARCHAR(MAX)
SET @SQLTR=’
CREATE TRIGGER tg_’+@TABLENAME+’_Delete
ON ‘+@TABLENAME+’
AFTER delete
AS
BEGIN
SET NOCOUNT ON;
–==============================获取GUID==========================================
DECLARE @NEWID VARCHAR(36)=NEWID()
–==============================将删掉的数据插入备份表============================
INSERT INTO [dbo].[BACKUP_’+@TABLENAME+’]
SELECT @NEWID,* FROM deleted
–==============================记录日志和回滚操作的SQL===========================
–*********************生成列名**********************
DECLARE @COLUMN NVARCHAR(MAX)=””
SELECT @COLUMN+=”,[”+COLUMN_NAME+”]” FROM INFORMATION_SCHEMA.columns
WHERE TABLE_NAME=”’+@TABLENAME+”’
AND COLUMNPROPERTY(OBJECT_ID(”’+@TABLENAME+”’),COLUMN_NAME,”IsIdentity”)<>1 –非自增字段
SET @COLUMN=SUBSTRING(@COLUMN,2,LEN(@COLUMN))
INSERT INTO [dbo].[UPDATE_LOG]
SELECT @NEWID,GETDATE(),”’+@TABLENAME+”’,”DELETE”,”INSERT INTO ‘+@TABLENAME+’ SELECT ”+@COLUMN+” FROM BACKUP_’+@TABLENAME+’ WHERE UPDATEGUID=”””+@NEWID+””””
END
‘
EXEC(@SQLTR)
END
END
接着我们新建一张测试表，并且随便往表中插入两组数据：
Create table test
(
id int,
name varchar(10),
msg varchar(10)
)
Insert into test
Select 1,’aa’,’hahah’
Union all
Select 2,’bb’,’heihei’
下面执行这个SP,在给test表添加回滚日志：
EXEC SP_DELETE_LOG ‘test’
细心的你不难发现，这时候数据库里面应该会多出两张表：
然后我们删掉一条数据：
DELETE FROM test WHERE id=1
再查看那两张表：
没错，这时候日志表里有数据了，然后我们把 UPDATE_LOG 表中的 RollBackSQ L这一列对应的值copy出来执行一下：
INSERT INTO test SELECT [id],[name],[msg] FROM BACKUP_test WHERE UPDATEGUID=’B0CBBC4F-3432-4D4F-9E17-F17209BF6745′
别copy我上面这段sql，因为GUID肯定是不一样的！
然而，数据恢复了：
最后，delete日志的介绍就结束了，唯一的不满足的是只能作用在Delete 操作，其实UPDATE 操作也同样需要这样的回滚日志。
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。如有错误或未考虑完全的地方，望不吝赐教。
