MS Access error 3259, which says "Invalid field data type," often happens when you're updating or accessing fields in an Access database.

Correcting the object name to match the actual Lakehouse name used in the exercise instead of [ExternalData]. Here is the link to the exercise where I encountered the issue: MS Fabric Tutorial ...

Higher Testing Syntax, execution and logic errors Programmers often encounter logic, syntax and execution errors and use dry runs, trace tables and breakpoints to resolve errors and finalise code.