What is the meaning of the error message "duplicate key value violates unique constraint" in Django?

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The error message "duplicate key value violates unique constraint" in Django means that an attempt was made to insert or update a record in the database with a value in a field that already exists in another record and is supposed to be unique. This violates the unique constraint set on that field, and the database rejects the operation, resulting in the error message. To fix this error, the duplicate value must be removed or updated so that it no longer violates the unique constraint.