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 #