Update SQL using Coldfusion

Hi
Im trying to create an UPDATE Query in coldfusion so I can run it in a schedule every hr

Ive been trying the below but it doesnt seem to like it

<cfquery name="test" datasource="#test1#">
	Update INVOICE, CUSTOMER
	SET C.CUSTOMER_Email = I.CUSTOMER_Email
	where C.CUSTOMER_AccNum = I.CUSTOMER_AccNum	
	AND C.CUSTOMER_DevlNum = I.CUSTOMER_DelvNum
	AND C.COMPANY_Number = I.COMPANY_Number
</cfquery>

Where is C and I being defined?

Should it not be Invoice as I, Customer as C

coldfusion has nothing to do with this, the correct syntax for a joined update depends on which database system this is, which you neglected to mention