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Oracle -
Explain the different types of queries in Oracle - April 10, 2009
at 11:00 AM
Explain the different types of queries in
Oracle.
Session Queries are implicitly constructed and
executed by a Session based on input parameters.Input parameters are
used to perform the most common data source actions on objects.
Database Queries are created and then executed
to perform any data source action on either objects or data. They
can be further refined by also creating and configuring its
Call.
Named Queries can be executed repeatedly by
name. They are an instance of DatabaseQuery stored by name in a
Session or a descriptor's DescriptorQueryManager where it is
constructed and prepared once.
Call Queries are instances of Call that are
created and then either executed directly or indirectly in the
context of a DatabaseQuery.
Redirect Queries are instances of
MethodBasedQueryRedirector set on a named query. When the query is
executed, the static method is invoked.
Historical Queries are queries executed in the
context of a historical session using the time-aware features of the
TopLink Expression framework.
Interface and Inheritance Queries are queries that references an
interface type or super and subclasses of an inheritance hierarchy.
Also read
A query which uses values from the outer query is called as a
correlated sub query. The subquery is executed once and uses the
results for all the evaluations in the outer query.............
Explain sub-queries in brief, What are the different operators
used in building sub queries?, What are the guidelines for using
SUB-QUERIES?, What is correlated sub-query?............
Oracle engine uses private working area to process queries. This
work area is called as cursor. The
data that is stored in the cursor is called as Active
Data Set..............
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