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Turning on Use Remote Collation did the trick. Initially it didn't, but I set it when I had query analyser open, so its possible...

Happycat59,

I've set the collation cimpatible option. It was suggested in a microsoft "Optimising Distributed queries" article. Should I select "Use Remote Collation" too? I have tested the basic query inside...

OpenRowset and OpenQuery were proving stressful. Because I was passing in an input variable into the query I had to throw an EXEC round the command, and then the whole...

I'm basing the time calculation running the query through query analyser without the function wrapping, and using a literal Patient ID

I.e.

Select DOB from Birmb91s.Demographics.dbo.Demographics Where Patient_ID='123456'

And this is about 6m45s...