Amazon SimpleDB is a web service providing the core database functions of
data indexing and querying in the cloud. By offloading the time and effort
associated with building and operating a web-scale database, SimpleDB
provides developers the freedom to focus on application development.
A traditional, clustered relational database requires a sizable upfront
capital outlay, is complex to design, and often requires extensive and
repetitive database administration. Amazon SimpleDB is dramatically simpler,
requiring no schema, automatically indexing your data and providing a simple
API for storage and access. This approach eliminates the administrative
burden of data modeling, index maintenance, and performance tuning.
Developers gain access to this functionality within Amazon's proven
computing environment, are able to scale instantly, and pay only for what
they use.
Specifies the conditions under which data should be updated. If an update
condition is specified for a request, the data will only be updated if the
condition is satisfied. For example, if an attribute with a specific name
and value exists, or if a specific attribute doesn't exist.
