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Manual
11

DELETE Queries in JPA/JPQL

. For example, the EntityManager may not be aware that a cached entity object in its persistence ... of subclasses) from the database. For example, the following three equivalent queries delete all the Country ... . A WHERE clause, which is essential for removing selected entity objects, is supported. For example
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11

Deleting JPA Entity Objects

(cascade=CascadeType.REMOVE) private Address address; : } In the example above, the Employee ... . The difference between the two settings is in the response to disconnecting a relationship. For example ... objects. Orphan removal can also be set for collection and map fields. For example: @Entity class
Manual
11

GROUP BY and HAVING clauses

calculations - the GROUP BY functions merely as a DISTINCT operator. For example, the above query ... which all the FROM/WHERE objects (or object tuples) are considered as one group. For example ... for setting the GROUP BY and HAVING clauses. For example, the following JPQL query: SELECT c
JPA Doc
11

JPA Exceptions

the PersistenceException class. Some specific errors are represented by subclasses of PersistenceException. For example ... ) . For example, if a transaction fails because of an attempt to store a new entity object with a primary ... to retrieve entity objects from the database. For example, when a required entity object is not found: or
Manual
11

JPA Primary Key

primary key fields. Each primary key field must be one of the supported types listed above. For example ... ) of a specified managed entity object. For example: PersistenceUnitUtil util = emf ... useful when using queries that return large result sets. As an example, consider a real time
Manual
11

Locking in JPA

a PESSIMISTIC_READ lock on that database object. For example, consider the following code fragment: em1 ... one atomic operation. For example, the find method has a form that accepts a lock mode: Employee ... operation includes pessimistic locking, timeout can be specified as a property. For example
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11

Online Backup

file itself is created in that subdirectory with the name of the original database file. For example ... , and in client-server mode, relative to the ObjectDB home directory on the server side. For example, in ... a Thread instance that represents the backup run. This thread can be used, for example, for waiting
Manual
11

ORDER BY clause (JPQL / Criteria API)

, for example, is invalid because the ORDER BY expression is not part of the results: SELECT c.name ... can order these groups. For example: SELECT c.currency, SUM(c.population) FROM Country c ... provides methods for setting the ORDER BY clause. For example, the following JPQL query: SELECT c FROM
Manual
11

Setting and Tuning of JPA Queries

. These methods support the implementation of efficient result paging. For example, if each result ... that has to be applied on all the result objects that the query retrieves. For example, the following query ... all the queries in that scope (unless it is overridden in a more local scope). For example, setting a query
Manual
11

Shared (L2) Entity Cache

classes except classes that are specified as Cacheable explicitly. For example: @Cacheable // or ... that are specified as non Cacheable explicitly. For example: @Cacheable(false) @Entity public class ... can also be overridden for a specific retrieval operation. For example: em.find(MyEntity2.class