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391

answers:

3

I'm writing a script that is supposed to run around a bunch of servers and select a bunch of data out of them, including the local server. The SQL needed to SELECT the data I need is pretty complicated, so I'm writing sort of an ad-hoc view, and using an OPENQUERY statement to get the data, so ultimately I end up looping over a statement like this:

exec('INSERT INTO tabl SELECT * FROM OPENQUERY(@Server, @AdHocView)')

However, I've heard that using OPENQUERY on the local server is frowned upon. Could someone elaborate as to why?

A: 

check linked servers

Andrey
+3  A: 
  • Although the query may return multiple result sets, OPENQUERY returns only the first one.
  • OPENQUERY does not accept variables for its arguments.
  • OPENQUERY cannot be used to execute extended stored procedures on a linked server. However, an extended stored procedure can be executed on a linked server by using a four-part name.
  • If the sp_addlinkedserver stored procedure is used within same script, the credentials used on the remote server are hardcoded into the script, visible to anyone who has a copy

Reference:

OMG Ponies
I happened to have occasion to use `OPENQUERY` the other day and realized your 4th point was incorrect; `OPENQUERY` operates on a linked server so no credentials are hard-coded. You may be thinking of `OPENROWSET`.
Aaronaught
@Aaronaught: If a linked server instance exists, why use OPENQUERY at all? If the `sp_addlinkedserver` stored procedure is used within the same script, my point has merit.
OMG Ponies
Well, since you asked, there actually is a reason to use `OPENQUERY`: Performance. `OPENQUERY` allows the query to be processed on the remote server, whereas standard 4-part naming has to copy all the rows to the local server, which is pretty bad for large data sets. Of course this has to be weighed against the other trade-offs you've mentioned.
Aaronaught
+1  A: 

In addition to what @OMG Ponies said, it's simply unnecessary. There's no reason to introduce ad-hoc query and distributed transaction semantics when you don't have to. When you use OPENQUERY you take on all of the negative aspects of dynamic SQL, including less predictable plans and the server's inability to accurately track dependencies.

OPENQUERY also requires the local user to have permissions to the target server, which is probably not what you want unless it's an administrative script. You can't expect every user of one database to have the same permissions to every other database.

Aaronaught