One of the ways to update features in a database is by using the FME format attribute fme_db_operation. The attached workbench (fme_db_operation.fmwt) illustrates the use of this to update or delete features from a database.
The steps involved are:
test the incoming features for a value which will determine whether the feature is an update, delete or insert
add the attribute fme_db_operation to the features and assign it a value - either UPDATE/DELETE/INSERT
set the UPDATE KEY COLUMN to an attribute that will match the input features to the database features - in this case it is the attribute "ID". For writers that do not have the Update Key Field use the fme_where format attribute
change the WRITER MODE on the destination dataset to UPDATE (this causes the writer to recognize the fme_db_operation attribute)
The FME Format Attribute, fme_db_operation, is available on most of the database readers and writers. See the FME User Documentation for the database you're using.
The second sample workspace illustrates use of writer mode on the feature type - see DataBaseWriterMode.fmwt. Our recommendation is to use the fme_db_operation approach to database updates.