SQL事务日志还原实例

USE master
GO
-- 创建测试数据库
CREATE DATABASE db_test GO

-- 对数据库进行备份
BACKUP DATABASE db_test
TO DISK = 'c:/db_test.bak'
WITH FORMAT
GO

-- 创建测试表
CREATE TABLE db_test.dbo.tb_test(
ID int)

-- 延时 1 秒钟,再进行后面的操作(这是由于SQL Server的时间精度最大为百分之三秒,不延时的话,可能会导致还原到时间点的操作失败)
WAITFOR DELAY '00:00:01'
GO

-- 假设我们现在误操作删除了 db_test.dbo.tb_test 这个表
DROP TABLE db_test.dbo.tb_test
GO

--在删除操作后,发现不应该删除表 db_test.dbo.tb_test

--下面演示了如何恢复这个误删除的表 db_test.dbo.tb_test

--首先,备份事务日志(使用事务日志才能还原到指定的时间点)
BACKUP LOG db_test
TO DISK = 'c:/db_test_log.bak'
WITH FORMAT
GO

-- 获取可尝试的时间范围
IF OBJECT_ID(N'tempdb..#') IS NOT NULL
DROP TABLE #
CREATE TABLE #(
BackupName nvarchar(128) ,
BackupDescription nvarchar(255) ,
BackupType smallint ,
ExpirationDate datetime ,
Compressed tinyint ,
Position smallint ,
DeviceType tinyint ,
UserName nvarchar(128) ,
ServerName nvarchar(128) ,
DatabaseName nvarchar(128) ,
DatabaseVersion int ,
DatabaseCreationDate datetime ,
BackupSize numeric(20,0) ,
FirstLSN numeric(25,0) ,
LastLSN numeric(25,0) ,
CheckpointLSN numeric(25,0) ,
DatabaseBackupLSN numeric(25,0) ,
BackupStartDate datetime ,
BackupFinishDate datetime ,
SortOrder smallint ,
CodePage smallint ,
UnicodeLocaleId int ,
UnicodeComparisonStyle int ,
CompatibilityLevel tinyint ,
SoftwareVendorId int ,
SoftwareVersionMajor int ,
SoftwareVersionMinor int ,
SoftwareVersionBuild int ,
MachineName nvarchar(128) ,
Flags int ,
BindingID uniqueidentifier ,
RecoveryForkID uniqueidentifier ,
Collation nvarchar(128) ,
FamilyGUID uniqueidentifier ,
HasBulkLoggedData bit ,
IsSnapshot bit ,
IsReadOnly bit ,
IsSingleUser bit ,
HasBackupChecksums bit ,
IsDamaged bit ,
BeginsLogChain bit ,
HasIncompleteMetaData bit ,
IsForceOffline bit ,
IsCopyOnly bit ,
FirstRecoveryForkID uniqueidentifier ,
ForkPointLSN numeric(25,0) NULL,
RecoveryModel nvarchar(60) ,
DifferentialBaseLSN numeric(25,0) NULL,
DifferentialBaseGUID uniqueidentifier ,
BackupTypeDescription nvarchar(60) ,
BackupSetGUID uniqueidentifier NULL
)
INSERT # EXEC(N'
RESTORE HEADERONLY
FROM DISK = ''c:/db_test.bak''
WITH FILE = 1
RESTORE HEADERONLY
FROM DISK = ''c:/db_test_log.bak''
WITH FILE = 1
')
--SELECT
-- *
--FROM #

-- 定义尝试的时间范围，以及尝试时间点的间隔
DECLARE
@start_date datetime,
@stop_date datetime,
@try_step_millsecond int,
@msg nvarchar(1000)
SELECT
@start_date = MIN(BackupFinishDate), -- 尝试查找误删除数据的开始时间
@stop_date = MAX(BackupFinishDate), -- 尝试查找误删除数据的结束时间
@try_step_millsecond = 500 -- 每 500 毫秒为一个时间点找一次数据
FROM #

-- 还原完全备份
RESTORE DATABASE db_test
FROM DISK = 'c:/db_test.bak'
WITH REPLACE,
NORECOVERY

-- 还原日志备份到各点，以寻找出所需数据
WHILE @start_date < @stop_date
BEGIN
SELECT
@start_date = DATEADD(ms, @try_step_millsecond, @start_date),
@msg = N'尝试时间点: ' + CONVERT(varchar(50), @start_date, 121)

RAISERROR(@msg, 10, 1) WITH NOWAIT
BEGIN TRY
-- 还原日志到指定的点，并通过 STANDBY 使数据库能只读访问
RESTORE LOG db_test
FROM DISK = 'c:/db_test_log.bak'
WITH STOPAT = @start_date,
STANDBY = 'c:/db_test_redo.bak'

-- 检查需要的数据是否存在
IF OBJECT_ID(N'db_test.dbo.tb_test') IS NOT NULL
BEGIN
-- 显示还原的时间点
SELECT Restoreto = @start_date
-- 完成数据库还原，使数据库可读写
RESTORE LOG db_test
WITH RECOVERY

SELECT
@start_date = @stop_date
END
END TRY
BEGIN CATCH
END CATCH
END
GO

--最后删除测试环境
DROP DATABASE db_test
DROP TABLE #