What does JPA @UniqueConstraint do in Hibernate?

Question

In Hibernate, why should I use the JPA tag:

@Table(name=\"tbl_sky\",
    uniqueConstraints = {@UniqueConstraint(columnNames={\"month\", \"day\"})}
)

Answer 1

It helps hibernate in schema generation (DDL) for your mappings. Look at: http://docs.oracle.com/javaee/6/api/javax/persistence/UniqueConstraint.html