March 2008
Intermediate to advanced
604 pages
18h 38m
English
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Performing Queries
The SimpleDB service allows you to perform queries on your data through a Query API operation. The service only understands queries that are expressed in a simple query language that is specific to SimpleDB. These queries include a set of attribute predicates that are compared against the items stored in one of your domains. The names of items that satisfy all of the predicates are returned by the Query operation.
The SimpleDB Query operation and query language work very differently than the Structured Query Language (SQL) that is supported by relational databases. These differences can add to the complexity of applications that use the SimpleDB service, because the application may be required to do more work to retrieve, organize, and interpret the results of query operations than is normally the case. There are four key areas in which your applications may have to make up for shortcomings in the SimpleDB query language and API.
- Query results do not include attribute values
When you perform a SimpleDB query operation, the service returns a list of items that match the query. The matching items are identified by their names in the query results, but this is the only information returned by the service; none of the items’ attribute names or values are included. This means that client applications must perform follow-up GetAttributes operations (see Retrieve an Item’s Attributes”) to retrieve the actual attribute data associated with each result item. If you perform ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.