Hey, I have a multiselect field which refers to Item records. When I retrieve it using REST it returns the internal IDs of those items. But the external system which is calling the REST API doesn't know what they represent. Is there any way to make it return externalIDs or names?

What difference will it make? You get internal ID and work with that.

REST webservices. The calling system does not know what Item's internal IDs represent, it holds externalIds for Items.

The calling system probably needs to make another call to get the related external IDs based on the Internal IDs that you are getting.

Yeah, I was hoping to avoid making a second call. But seems it's probably the best way.

You do use a SuiteQL query to get everything in one call

A JOIN in SuiteQL would return one row for each entry in the multi select. I need one row per record

You could use GROUP BY

No, because SuiteQL doesn't have any aggregate functions that work on strings as far as I can tell.

Did you try? I haven't had issues with that in the past

Try what? There isn't an aggregate function to try?