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UniqueConstraint

Treimin Clark
Ranch Hand

Joined: Nov 12, 2008
Posts: 757
HeadFirst EJB 3.0 Book wrote:The @Table.UniqueConstraint attribute allows you to specify unique column constraint.


JPA Specs- (9.1.4) wrote:The UniqueConstraint annotation is used to specify that a unique constraint is to be included in the generated DDL for a primary or secondary table.


But I didn't understand what is this "unique column constraint"


Christophe Verré
Sheriff

Joined: Nov 24, 2005
Posts: 14688
    
  16

It allows to generate unique constraints in the DDL. Unique constraints are explained here. (I don't think this kind of annotation is at the exam, but who knows...)


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Treimin Clark
Ranch Hand

Joined: Nov 12, 2008
Posts: 757
Christophe Verré wrote:It allows to generate unique constraints in the DDL. Unique constraints are explained here. (I don't think this kind of annotation is at the exam, but who knows...)


Thanks Christophe
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: UniqueConstraint