Amazon SimpleDB Limitations
In the Write to DB stage, the write mode Update
is not available when writing to an Amazon SimpleDB table. The Insert
option handles both insert and update operations. It differentiates between an insert and an
update using the unique value of the ItemName
column which is present in
all Amazon SimpleDB tables.
This limitation is due to the fact that an update query requires a Primary Key for each record of the table to be updated, which is not supported by Amazon SimpleDB databases.