•FedSQL can perform heterogeneous correlated subqueries. A correlated subquery is
when the outer query results affect the results of the subquery. FedSQL has the
ability to direct a subquery to be performed by the data source and limit the result set
that is transferred from the data source. This is done by using a flexible query
textualization technique that allows FedSQL to obtain rows that only satisfy the
subquery expression. For an example, see “Example 4: Querying Data Using a
Correlated Subquery” on page 779.
•A unique way that FedSQL can perform a heterogeneous operation is to take
advantage of an index in a third-party DBMS when performing ...
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