Stored Procedure to change default

Can someone explain to me why the following doesn't work?

declare @oname sysname
select @oname=name from sysobjects where name like
"df__mytable__mycol%"

alter table mytable drop constraint @oname

Maybe more than one row is returned, and only one value can fit into a
variable.

This will work:

declare @oname sysname
select TOP 1 @oname=name from sysobjects where name like
"df__mytable__mycol%"

alter table mytable drop constraint @oname

Regards
--------------------------------
Mike Epprecht, Microsoft SQL Server MVP
Zurich, Switzerland

IM: mike@epprecht.net

MVP Program: http://www.microsoft.com/mvp

Blog: http://www.msmvps.com/epprecht/

<JLavalley@Enlighten.Net> wrote in message
news:1134587099.580770.161300@g44g2000cwa.googlegroups.com...
> Can someone explain to me why the following doesn't work?
>
> declare @oname sysname
> select @oname=name from sysobjects where name like
> "df__mytable__mycol%"
>
> alter table mytable drop constraint @oname
>

Thanks, but that didn't do it.  I get the same error:

Line 3: Incorrect syntax near '@oname'

(JLavalley@Enlighten
.Net)  writes:
> Can someone explain to me why the following doesn't work?
>
> declare @oname sysname
> select @oname=name from sysobjects where name like
> "df__mytable__mycol%"
>
> alter table mytable drop constraint @oname

Why should it work? There are some places you can use variables in
T-SQL for object names, but in most places you can't. Check out the
syntax chart in Books Online when in doubt.

You can use dynamic SQL: EXEC('ALTER TABLE tbl DROP CONSTRAINT ' + @oname)

For more information about dynamic SQL, see this article on my web site:
http://www.sommarskog.se/dynamic_sql.html.

--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se

Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/pr...oads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodin...ions/books.mspx

>Why should it work?<
What kind of question is that?  Not relevant here.  I asked why it
doesn't...

thank you for your response, not only did you solve my problem (using
"exec") but you educated me on the fact that I can't use variables for
object names in most places.

PS.
It should work because it's much more intuitive than having to create
and execute a string of the same command.
It should work because that would be consistant with other T-SQL
commands