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Comparison in JPQL and Criteria API

. JPQL follows the SQL notation, where Java uses its own notation (which is also in use by JDOQL ... , there is also a difference in the way that NULL values are handled by these operators. Comparing NULL values The following table shows how NULL values are handled by each comparison operator. One column presents

JPA Queries

three groups. SELECT and ORDER BY elements (including tuples): FROM clause elements (representing range ... Queries are represented in JPA by the Query and TypedQuery interfaces: The JPA Query API section ... only at runtime (e.g. depending on which fields are filled by a user in a form) can be done by

Criteria Query Selection and Results

The JPA Criteria API interfaces in this group are used for setting the SELECT and ORDER BY clauses ... clause in a criteria query is represented by Selection: Because Selection is a super interface ... expressions can be represented by CompoundSelection, which is itself a subinterface of Selection


queries cannot include the GROUP BY, HAVING and ORDER BY clauses, but the WHERE clause ... Existing entity objects can be updated, as explained in chapter 2, by: Retrieving the entity ... . Applying changes to the database by calling the commit method. JPQL UPDATE queries provide


multiple variables and JOIN, and cannot include the GROUP BY, HAVING and ORDER BY clauses ... As explained in chapter 2, entity objects can be deleted from the database by: Retrieving ... transaction, either explicitly by calling the remove method or implicitly by a cascading operation

JPA Criteria API Queries

). FROM clause (from, join, fetch). WHERE clause (where). GROUP BY / HAVING clauses (groupBy, having ... , are defined by the instantiation of Java objects that represent query elements. A major advantage ... factory of criteria queries and criteria query elements. It can be obtained either by

JPA Persistence Unit

A JPA Persistence Unit is a logical grouping of user defined persistable classes (entity classes ... is optional when using ObjectDB, but required by JPA. persistence.xml Persistence units are defined in ... > </persistence-unit> </persistence> A persistence unit is defined by a persistence-unit XML element

Criteria Query From Elements

The interfaces in this group are in use for setting a criteria query FROM clause. Criteria Query ... are represented in criteria queries by descendant interfaces of the From interface: Range variables (bound by an entity class) are represented by the Root subinterface: Join variables (bound by


to the type specified by the resultClass argument. Parameters: name - the name of a query defined in ... item, which must be assignable to the type specified by the resultClass argument. Parameters: qlString ... or is managed by another PersistenceManager. Parameters: pc - a persistent instance Since: JDO 1.0


the PersistenceManagerFactory (recommended) or by construction. Since: JDO 1.0 void ... JDOUserException if the instance is transient or is managed by another PersistenceManager. Parameters: pc ... (DETACH_LOAD_FIELDS and DETACH_UNLOAD_FIELDS) and the active fetch groups determine the scope

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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