Queries and Expressions

TopLink provides several object and data query types, and offers flexible options for query selection criteria, including the following:

• TopLink expressions

• EJB QL

• SQL

• Stored procedures

• Query by example

With these options, developers can build any type of query. Oracle recommends using predefined queries to define application queries. Predefined queries are held in the project metadata and referenced by name. This simplifies application development and encapsulates the queries to reduce maintenance costs.

When using EJB entity beans, you can code finders using only EJB QL (in addition to any of the other TopLink query options), enabling the application to comply with the J2EE specification.

Regardless of the architecture or persistent entity type, you are free to use any of the query options. TopLink Workbench provides the simplest way to define queries. Alternatively, you can build queries in code, using the TopLink API.

For more information, see the following:

• "Understanding TopLink Queries"

• "Understanding TopLink Expressions"