How can i use Variable?

Try putting quotes around variable name

<ATEUserName> = John Smith

SELECT * from md_orders Where createdby = John Smith << Fails
SELECT * from md_orders Where createdby = 'John Smith' << Works

This with quotes works fine in where clause but not if ingested as variable in function ..

Does it work in SQL server management studio?

With simple SQL not .. i use this code
this work fine .. ok I'll try to find another solution ..

Thank you very much for your help!

Peter

how about this one?
SELECT lmxdatsk.fRegisterOrder('AAS') AS IdOrder
FROM md_orders