I believe this will do what you want.
<cfquery name="q1" datasource="myDsn">
update table1
set field1 = '#textValue#'
where recordID = #recNum#
</cfquery>
If the field is a numeric field, change the ='textValue' to = #numberValue#. You put single quotes around text values and leave them off for numeric or date values. If you want to update all the rows and not just a single row, leave off the "where recordID = #recNum#".
Hope this helps,
GJ