@noob, I just tried it on my local SQL Server instance and it worked as expected. I’m running IS 10.11 with Core Fix 4 with MS SQL JDBC driver 9.4.1 against a SQL Server Express 15 instance. I have a simple table called “people” with a column called “firstName”. When I ran: select firstName from people
This was my output:

Then when I ran: select firstName as fn from people
This was my output:

I’m guessing you may be running into incompatibility issues. Perhaps you require an updated JDBC driver or a fix to be applied to the JDBC adapter. Feel free to share the IS version and patch level along with the JDBC driver version and database vendor/version, and perhaps we can assist further.
Hope this helps,
Percio
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