Answer
Double-check the exact spelling of every view/table name referenced in the Select Statement, character by character — an Invalid Expression error on an otherwise reasonable-looking statement is very often a simple typo in a view name (for example, 'equpiment_object' instead of 'equipment_object') rather than a genuine logic or syntax problem. Custom field validation doesn't always point directly at the misspelled identifier, so a careful re-read of every referenced object name is the fastest way to catch this class of error.