MySQL has this incredibly useful yet proprietary REPLACE INTO
SQL Command.
Can this easily be emulated in SQL Server 2005?
Starting a new Transaction, doing a Select()
and then either UPDATE
or INSERT
and 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?
Both MySQL and SQL Server are developed as binary collections. But, SQL Server is far more secure than MySQL. MySQL allows developers to access and manipulate files in the database through binaries at run time. Plus, it also allows other processes to access and modify files at run time.
After 10 great years, extended support for all versions of SQL Server 2005 is coming to an end on April 12, 2016.
SQL Server allows canceling query execution midways. MySQL blocks the database while taking the backup. SQL Server does not block the database during backup process. MySQL is free to use.
This is something that annoys me about MSSQL (rant on my blog). I wish MSSQL supported upsert
.
@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 update
or insert
)
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 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. It's really easy to get primary key violations or duplicate rows in production.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With