Hi,

We are using Talend middleware to integrate and exchange data between our internal systems and SF using SF API. The SF CRM is acting as a 'slave' while our system database is a master.  So, almost every object in SF has an external ID that maches the record in our DB. 

All our 'upserts' works fine when matched on External ID. But in this case, we need to update - not upsert - the record in SF using External ID, which is marked as unique in SF. 

But, when runing the code this is the error: MISSING_ARGUMENT:Id not specified in an update call - for every single record regardles if the External ID already exist in SF or not.

So, my question is - can update be done on External ID or it must be the SF Id ?

Thanks