Sql-server – How to schedule a weekly backup of a database only if it has been changed since last backup

This procedure should do what you want:

create procedure dbo.dbrestore
@dbname nvarchar(50)
as
declare @fileno integer
declare @dumpdevice nvarchar(50)
declare @mediasetid integer
declare @position integer

select top(1) @dumpdevice=a.logical_device_name, @mediasetid=b.media_set_id, @position=b.position from backupmediafamily a inner join backupset b on a.media_set_id=b.media_set_id
where b.database_name='backuptest' and b.type='D' order by a.media_set_id desc, b. position desc

declare restore_cursor cursor for
select position from msdb.dbo.backupset where database_name=@dbname and type='D' and media_set_id=@mediasetid and position=@position
union
select  max(position) as position from msdb.dbo.backupset where database_name=@dbname and type='I' and media_set_id=@mediasetid and position>@position
union
select position from msdb.dbo.backupset where database_name=@dbname and type='L' and media_set_id=@mediasetid and position>@position
and last_lsn>(select max(last_lsn)from msdb.dbo.backupset where database_name=@dbname and type='I' and media_set_id=@mediasetid and position>@position)
order by position asc;

open restore_cursor
fetch next from restore_cursor into @fileno
while @@FETCH_STATUS = 0
begin
--comment the print statement and uncomment the exec statement to run
--exec('restore database ['+@dbname+'] from '+@dumpdevice+' with norecovery, replace, FILE='+@fileno+';')
  print ('restore database ['+@dbname+'] from '+@dumpdevice+' with norecovery, replace, FILE='+convert(varchar(4),@fileno)+';')
fetch next from restore_cursor into @fileno
end
close restore_cursor
deallocate restore_cursor
--exec('restore database ['+@dbname+'] with recovery;')
go

execution goes:

get the name of the dumpdevice based on the supplied database name. I'm assuming that they are all on the same device. The top is to work around having multiple media sets per database if using 'with format' for the initial DB, and to cope with the possibility of multiple full backups in the device

Then build up a union query consisting of:

The last full database backup (type=D) in the device

the last differential backup (type=I and has the greatest LSN (Log Sequence Number)) taken after the last full db backup.

the transaction logs (type=L) taken after the above diff.

returning just the position value, which maps to the FILE value in this case (http://msdn.microsoft.com/en-us/library/ms186299.aspx)

Loop through the result restoring them individually, and then a final restore with recovery to finish it off.

Call it as:

exec dbrestore 'db2restore'

I've tried it on a test db and it appears to work happily, and comparing it to the files SSMS wants to restore for the same operation it looks the same.

Provided as is, there's probably typos, I've probably missed a possible boundary condition, and there's no error checking.

You can use a 3rd party tool like Red-Gate SQL Compare. It has a command-line interface that you can easily invoke using cmd or PowerShell (and you can do these from a SQL Server job, but you don't necessarily need to saddle SQL Server Agent with this task - you can just as easily do it using Windows scheduled tasks or a PowerShell job).

You can use your script to tell the tool to compare your source database with an intentionally empty database every night and either:

• save the script somewhere, or
• create a new database, apply the script, backup the new database and drop it.

(Depending on whether you want a script of the schema or an actual empty database that looks like your real database.)

That isn't the only tool to use, of course, but it's the one I have the most experience with. I know that it works and I know they invested in the command-line tool for exactly this purpose. You can check out some other potential offerings here:

• Re-Blog : The cost of reinventing the wheel

You may also see if tools like Visual Studio SSDT (which replaces Visual Studio Team Edition for Database Professionals) does this - you may already have a workable solution in house. I haven't done much with SSDT yet so can't be sure its schema comparison features are scriptable.