RE: Inventory Serial Number

what are you looking for ? Do you need to join these tables and get the serial Id as display field in SalesLine in Ax ?

Try this .

InventDim::find(SalesLine.InventDimId).inventSerialId

or

Select firstOnly inventDim

               Join salesLine

               where inventDim.inventDimId == salesLine.InventDimId;

info(inventDim.inventSerialId);