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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"foreign key properties","articleBody":"I propose to allow specification of foreign key properties `unique` and `required`.\r\n\r\nI propose the following syntax.\r\n\r\n```\r\n-\u003e [unique, nullable] lab.Animal \r\n```\r\n\r\n\"Unique\" means that each animal in `lab.Animal` can be referenced only once from the referencing table.\r\n\r\n\"Optional\" means that the foreign key values can be null.  When null, the unique constraint is not applicable. \r\n\r\nBy default, foreign keys are not unique and not optional. \r\n\r\nThis syntax is compatible with the syntax for renamed foreign keys:\r\n\r\n```\r\n(subject_id) -\u003e [unique] lab.Animal\r\n``` ","author":{"url":"https://github.com/dimitri-yatsenko","@type":"Person","name":"dimitri-yatsenko"},"datePublished":"2017-03-13T17:30:46.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/301/datajoint-python/issues/301"}