Yes, the data will come from an 'input' component, and the output component will automatically do what you tell it via the 'insert or update' or whatever you tell it.
However, the question I think you are trying to ask is: How do I select all the data I will NEED to update (from the input component)?
You can do this via a simple where clause in your input component, though for this to work as I will say in a moment you will need both the input table and the ouput table on the same database, if this is not so I have an idea to help with that also but it is a little more difficult and complicated so I will not say now.
As for the sql query, here is my example using tables one and two with columns id, alpha, beta and delta:
select one.id
,one.alpha
,one.beta
,one.delta
from one,two
where one.id = two.id
and (two.alpha <> one.alpha
or two.beta <> one.beta
or two.delta <> one.delta)
;
This code would only select data needed to be updated, you would then pass this data into the output component with 'Update' selected and it would do its thing
I hope this helps.