MySQL has this incredibly useful yet properitary
REPLACE INTO SQL Command.
I wonder: Can this easily be emulated in SQL Server 2005?
Starting a new Transaction, doing a
Select() and then either
COMMIT is always a little bit of a pain, especially when doing it in the application and therefore always keeping 2 versions of the statement.
I wonder if there is an easy and universal way to implement such a function into SQL Server 2005?
This is something that annoys me about MSSQL (rant on my blog). I wish MSSQL supported
@Dillie-O's code is a good way in older SQL versions (+1 vote), but it still is basically two IO operations (the
exists and then the
There's a slightly better way on this post, basically:
--try an update update tablename set field1 = 'new value', field2 = 'different value', ... where idfield = 7 --insert if failed if @@rowcount = 0 and @@error = 0 insert into tablename ( idfield, field1, field2, ... ) values ( 7, 'value one', 'another value', ... )
This reduces it to one IO operations if it's an update, or two if an insert.
MS Sql2008 introduces
merge from the SQL:2003 standard:
merge tablename as target using (values ('new value', 'different value')) as source (field1, field2) on target.idfield = 7 when matched then update set field1 = source.field1, field2 = source.field2, ... when not matched then insert ( idfield, field1, field2, ... ) values ( 7, source.field1, source.field2, ... )
Now it's really just one IO operation, but awful code :-(
The functionality you're looking for is traditionally called an UPSERT. Atleast knowing what it's called might help you find what you're looking for.
I don't think SQL Server 2005 has any great ways of doing this. 2008 introduces the MERGE statement that can be used to accomplish this as shown in: http://www.databasejournal.com/features/mssql/article.php/3739131 or http://blogs.conchango.com/davidportas/archive/2007/11/14/SQL-Server-2008-MERGE.aspx
Merge was available in the beta of 2005, but they removed it out in the final release.
What the upsert/merge is doing is something to the effect of...
IF EXISTS (SELECT * FROM [Table] WHERE Id = X) UPDATE [Table] SET... ELSE INSERT INTO [Table]
So hopefully the combination of those articles and this pseudo code can get things moving.
I wrote a blog post about this issue.
The bottom line is that if you want cheap updates ... and you want to be safe for concurrent usage. try:
update t set hitCount = hitCount + 1 where pk = @id if @@rowcount < 1 begin begin tran update t with (serializable) set hitCount = hitCount + 1 where pk = @id if @@rowcount = 0 begin insert t (pk, hitCount) values (@id,1) end commit tran end
This way you have 1 operation for updates and a max of 3 operations for inserts. so, if you are generally updating this is a safe cheap option.
I would also be very careful not to use anything that is unsafe for concurrent usage. Its really easy to get primary key violations or duplicate rows in production.