I am a DBA and my rebuild index job has failed with the error that "The CREATE UNIQUE INDEX statement terminated because a duplicate key was found for the object name and index name". The non clustered unique index is created on two columns and i see that these two columns have a duplicate value. My question is that how was the duplicate data inserted in to the table when it already had a non clustered unique index in place on these columns.
Please help me to understand this concept.