Multiple Attribute Queries
The previous examples show how to create expressions for single predicates. The
Amazon SimpleDB query language also supports constructing expressions across multiple predicates
using the intersection operator.
Multiple attribute queries work by producing a set of item names from each predicate and
applying the intersection operator. The intersection operator only
returns item names that appear in both result sets.
This section shows multiple attribute queries and their results.
Note
To view the source data for the queries, see Sample Query Data Set.
The following table shows some multiple attribute queries, how they are interpreted, and the results they return from the sample dataset.
| Select Expression | Description | Result |
|---|---|---|
select * from mydomain where Rating = '****' |
Retrieves all items that have a "****" Rating. |
0802131786, 1579124585 |
select * from mydomain where every(Rating) = '****' |
Retrieves all items that only have a "****" Rating. Items are not returned that have a multi-valued Rating attribute that contains any value other than '****.' |
0802131786 |
select * from mydomain where Keyword = 'Book' intersection Keyword = 'Hardcover' |
Retrieves all items that have a "Book" Keyword and a "Hardcover" Keyword. The first predicate produces 0385333498, 0802131786, and 1579124585. The second produces 1579124585. The intersection operator returns results that appear in both queries. |
1579124585 |
