Each attribute is a key/value pair, and the value is where you store the interesting stuff—your data! You can only store textual data in SimpleDB for now. There are some ways to get around it and store binary data in Amazon S3 and use metadata in SimpleDB to point to it. We will discuss the procedures for accomplishing this in Chapter 7, Storing Data on S3. The only restriction textual data has, with a larger implication, is that you must encode and decode values for other data types such as dates and numbers when storing and retrieving them for use in your application. In the next chapter, we will review how to encode and decode data correctly so that we can do sorting and comparison correctly even for data types such as numbers and dates.
One of the unique features of SimpleDB is the ability to have multiple values for a single attribute. These multiple values are actually stored by SimpleDB in such a way that you can query for each separately!