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Ranch Hand
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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"


 
Sheriff
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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...)
 
Treimin Clark
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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
 
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