This tutorial exercise demonstrates how to create a Schema that sends a query to a data source to retrieve data according to the data source’s specialized query syntax. Using SQL or another specialized query language (for example, salesforce.com’s SOQL), you can make a more targeted retrieval of data than simply reading a table, and you can request that the database perform certain aggregations, such as grouping and joining, on the data rather than doing those aggregations in the dataflow.

    In addition to the query Schema, a Read operator that can handle data returned by a query is required. This tutorial also demonstrates how to create a Query Operator Descriptor.