About primary key

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JPA Doc
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JPA Annotations for Classes

are useful in representing composite primary keys as explained in the Primary Key section of the ObjectDB manual.
JPA Doc
17

JPA Annotations for Value Generation

Automatically generated values are mainly useful for primary key fields, but are supported by ObjectDB also for regular (non primary key) persistent fields. At the field level, the @GeneratedValue with an optional GenerationType strategy is specified: The @GeneratedValue annotation
JPA Doc
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javax.persistence.PrimaryKeyJoinColumn

get methods) Specifies a primary key column that is used as a foreign key to join to another table ... to a primary table; and it may be used in a OneToOne mapping in which the primary key ... to have the same names as the primary key columns of the primary table of the superclass. Example
Forum
14

Getting Foreign Key

level primary key but i also nead to get foreign key which is belongs to header. WriteObjectQuery ... got pojo name query.getPrimaryKey() by using this i can get primary key now i nead to get foreighn ... How to get Foreign key using  org.eclipse.persistence.queries.WriteObjectQuery class
Result
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What is new in ObjectDB 2.0?

ObjectDB 2.0 supports many new features and improvements, including: Most of the features of the new JPA 2.0 and JDO 2.2 APIs. User defined IDs (primary key) and sequences. Support of unlimited index keys size. SQL like queries ("select from ... where ..."). Real non blocking multithreading in
Manual
14

JPA Persistable Types

, however, do not have an identity (primary key) of their own which leads to some limitations (e.g ... and arrays and keys and values in maps) are either null values or instances of persistable types. In
Forum
14

Can a Set<E> be a foreign key?

I have two classes, Cell and Character.  Basically, the cell is like a room, and contains a variable (private Set cellHeldCharacters;) which holds the IDs of the characters within the cell (The IDs are Primary Keys).  Can I use the Foreign Key annotation for the variable, or is it illegal
JDO Doc
13

javax.jdo.annotations.PrimaryKey

get methods) Annotation on a member to define it as a primary key member of a class or persistent interface using application identity. Also used to define the primary key columns of a secondary table. Corresponds to the xml element "primary-key". Since: JDO 2.1 String column Name of the column to use
JPA Doc
12

javax.persistence.JoinColumn

field of the referencing entity or embeddable class; "_"; the name of the referenced primary key ... : the name of the entity; "_"; the name of the referenced primary key column. Default value ... the collection. Default (only applies if single join column is being used): The same name as the primary key
JPA Doc
12

JPA Exceptions

) . For example, if a transaction fails because of an attempt to store a new entity object with a primary key that is already in use by another existing entity object, the nested exception is: Other common