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Deleting JPA Entity Objects

Existing entity objects can be deleted from the database either explicitly by invoking the remove method or implicitly as a result of a cascade operation. Explicit Remove In order to delete an object ... since disconnecting a relationship is not a remove operation. To avoid dangling references as a result
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Entity Management Settings

JDO and as "false" when using JPA. The on-persist attribute specifies whether cascading (as a result ... specifies whether cascading (as a result of either global or local setting) should be applied
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GROUP BY and HAVING clauses

The GROUP BY clause enables grouping of query results. A JPQL query with a GROUP BY clause returns properties of generated groups instead of individual objects and fields. The position of a GROUP BY ... which returns the first letters as result. ObjectDB is very flexible in allowing JPQL expressions anywhere in
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General Settings and Logging

data, such as query results that contain millions of objects. The <temp> element specifies temporary ... sockets become obsolete as a result of inactivity. The value is the timeout in seconds, where 0
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Locking in JPA

JPA 2 supports both optimistic locking and pessimistic locking. Locking is essential to avoid update collisions resulting from simultaneous updates to the same data by two concurrent users. Locking ... _WRITE); A lock mode can also be set for a query in order to lock all the query result objects
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javax.persistence.criteria.CriteriaBuilder

an all expression over the subquery results. Create an all expression over the subquery results. Parameters ... over the subquery results. Create an any expression over the subquery results. This expression is equivalent ... that will be applied to the results of the query execution. If the constructor is for an entity class
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javax.persistence.Query

back Since: JPA 1.0 int getFirstResult() The position of the first result the query object was set to retrieve. The position of the first result the query object was set to retrieve. Returns 0 if setFirstResult was not applied to the query object. Returns: position of the first result Since: JPA 2
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javax.persistence.Tuple

javax.persistence Interface Tuple Interface for extracting the elements of a query result tuple ... position in the result tuple. Get the value of the element at the specified position in the result tuple. The first position is 0. Parameters: i - position in result tuple Returns: value of the tuple
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javax.persistence.criteria.CriteriaBuilder.Case

: may result in a runtime failure. Parameters: type - intended type of the expression Returns: new ... Since: JPA 2.0 Expression<R> otherwise(R result) Add an "else" clause to the case expression. Add an "else" clause to the case expression. Parameters: result - "else" result Returns: expression Since: JPA 2.0
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Step 4: Create an ObjectDB Data Set

): You may click Preview Results to see the query results: Close the dialog box by clicking the OK button. In

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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