T-SQL Recipes之Database Backups

The Problem

在DBA和T-SQL码奴日常工作中，比如常规检查，服务管理，数据库管理， 是其中最具挑战性的一个领域。

在相似任务中，比如索引碎片管理，统计管理，数据库备份是异常重要的，对任何程序而言。

今天的重点就是讲动态SQL数据库备份

假设我们的需要是根据一个时间点来决定三种不同类型的备份：Full backups, differential backups, transaction log backups.

我们可以假定

• Full backups: 一个星期备份一次
• differential backups: 每隔一天运行一次
• transcation log backups：每天运行一次

The Solution

问题描述的差不多了，现在咱们开动吧。

IF OBJECT_ID('dbo.backup_plan', 'P') IS NOT NULL
BEGIN
    DROP PROCEDURE dbo.backup_plan;
END
GO

CREATE PROCEDURE dbo.backup_plan
    @differential_and_full_backup_time TIME = '00:00:00', -- Default to midnight
    @full_backup_day TINYINT = 1, -- Default to Sunday
    @backup_location NVARCHAR(MAX) = 'D:\SQLBackups\', -- Default to my backup folder
    @print_output_only BIT = 1
AS
BEGIN
    SET NOCOUNT ON;

    DECLARE @current_time TIME = CAST(CURRENT_TIMESTAMP AS TIME);
    DECLARE @current_day TINYINT = DATEPART(DW, CURRENT_TIMESTAMP);

    DECLARE @datetime_string NVARCHAR(MAX) = FORMAT(CURRENT_TIMESTAMP , 'MMddyyyyHHmmss');

    DECLARE @sql_command NVARCHAR(MAX) = '';

    DECLARE @database_list TABLE
    (
      database_name NVARCHAR(MAX) NOT NULL ,
      recovery_model_desc NVARCHAR(MAX)
    );
    INSERT  INTO @database_list
            ( database_name ,
              recovery_model_desc
            )
            SELECT  name ,
                    recovery_model_desc
            FROM    sys.databases
            WHERE   databases.name NOT IN ( 'msdb', 'master', 'TempDB', 'model' );

    -- Check if a full backup is to be taken now.
    IF (@current_day = @full_backup_day) AND (@current_time BETWEEN @differential_and_full_backup_time AND DATEADD(MINUTE, 10, @differential_and_full_backup_time))
    BEGIN
        SELECT  @sql_command = @sql_command + '
         BACKUP DATABASE [' + database_name + ']
         TO DISK = ''' + @backup_location + database_name + '_' + @datetime_string
                + '.bak'';'
        FROM    @database_list;
    END
    -- Check if a differential backup is to be taken now.
    ELSE IF (@current_day <> @full_backup_day) AND (@current_time BETWEEN @differential_and_full_backup_time AND DATEADD(MINUTE, 10, @differential_and_full_backup_time))
    BEGIN

        SELECT @sql_command = @sql_command +
            '
            BACKUP DATABASE [' + database_name + ']
            TO DISK = ''' + @backup_location + database_name + '_' + @datetime_string +
            '.dif'' WITH DIFFERENTIAL;'
        FROM @database_list;
    END
    -- If neither full or differential, then take a transaction log backup
    ELSE
    BEGIN
        SELECT  @sql_command = @sql_command + '
           BACKUP LOG [' + database_name + ']
           TO DISK = ''' + @backup_location + database_name + '_' + @datetime_string
                + '.trn'''
        FROM    @database_list
        WHERE   recovery_model_desc = 'FULL';
    END

    IF @print_output_only = 1
    BEGIN
        PRINT @sql_command;
    END
    ELSE
    BEGIN
        EXEC sp_executesql @sql_command;
    END
END

从代码中可以看出，我们通过天数和时间点来判断三种不同类型的备份。我们还增加了一个只打印不运行的标志，现在我们来看看这三种不同类型的输出吧。

Full backups

EXEC dbo.backup_plan
    @differential_and_full_backup_time = '11:16:00',
    @full_backup_day = 2,
    @backup_location = 'D:\SQLBackups',
    @print_output_only = 1;

differential backups

EXEC dbo.backup_plan
    @differential_and_full_backup_time = '11:16:00',
    @full_backup_day = 3,
    @backup_location = 'D:\SQLBackups',
    @print_output_only = 1;

transcation log backups

EXEC dbo.backup_plan
    @differential_and_full_backup_time = '17:16:00',
    @full_backup_day = 3,
    @backup_location = 'D:\SQLBackups',
    @print_output_only = 1;

有了这个存储过程，以后我们备份数据库就方便许多了，当然你可以通过执行计划来备份的。