{"id":700,"date":"2019-01-23T21:43:33","date_gmt":"2019-01-23T12:43:33","guid":{"rendered":"https:\/\/www.nblog09.com\/w\/?p=700"},"modified":"2021-11-11T17:32:49","modified_gmt":"2021-11-11T08:32:49","slug":"django_on_delete","status":"publish","type":"post","link":"https:\/\/www.nblog09.com\/w\/2019\/01\/23\/django_on_delete\/","title":{"rendered":"django\u306e\u5916\u90e8\u30ad\u30fc\u3067\u6307\u5b9a\u3059\u308bon_delete\u306e\u30d1\u30e9\u30e1\u30fc\u30bf(PROTECT, SET_NULL, SET_DEFAULT, RESTRICT)\u307e\u3068\u3081"},"content":{"rendered":"

Django2\u7cfb\u4ee5\u964d\u306emodels.py\u304b\u3089\u5fc5\u9808\u306b\u306a\u3063\u305fon_delete\u306b\u3064\u3044\u3066<\/h2>\n

Django\u3067\u306f\u30012.0\u4ee5\u964d\u306e\u30d0\u30fc\u30b8\u30e7\u30f3\u3067\u3001\u30e2\u30c7\u30eb\u3092\u4f5c\u6210\u3059\u308b\u969b\u306b\u3001on_delete\u3068\u3044\u3046\u30d1\u30e9\u30e1\u30fc\u30bf\u3092\u6307\u5b9a\u3059\u308b\u3053\u3068\u304c\u5fc5\u9808\u306b\u306a\u3063\u305f\u3002<\/span><\/p>\n

on_delete\u3068\u3044\u3046\u306e\u306f\u3001model\u306eForeignKey\u3067\u5916\u90e8\u30ad\u30fc\u3092\u4f5c\u6210\u3059\u308b\u969b\u306b\u6307\u5b9a\u3057\u3001\u63a5\u7d9a\u5148\u306e\u30c6\u30fc\u30d6\u30eb\u306e\u30ec\u30b3\u30fc\u30c9\u304c\u524a\u9664\u3055\u308c\u305f\u5834\u5408\u306b\u3001\u63a5\u7d9a\u5143\u306e\u30ec\u30b3\u30fc\u30c9\u3092\u3069\u3046\u3059\u308b\u306e\u304b(\u524a\u9664\u3059\u308b\u306e\u304b\u6b8b\u3059\u306e\u304b)\u6c7a\u3081\u308b\u30d1\u30e9\u30e1\u30fc\u30bf\u3067\u3042\u308b\u3002<\/span><\/p>\n

\"\"<\/p>\n

on_delete\u3092\u8a2d\u5b9a\u3059\u308b\u306b\u306f\u3001models.py\u306e\u8a2d\u5b9a\u3067\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u8a18\u8f09\u3059\u308b\u3002<\/span><\/p>\n

\n

Example<\/h4>\n
    \n
  • models.py\u3067\u3001ForeignKey\u3092\u4f5c\u6210<\/li>\n<\/ul>\n
    \nfrom django.db import models<\/p>\n

    class Model1(models.Model):
    \n    model2 = models.ForeignKey(Model2, on_delete=models.CASCADE<\/span>) # CASCADE\u306e\u5834\u5408\u306b\u306f\u3001\u5916\u90e8\u30ec\u30b3\u30fc\u30c9\u3092\u524a\u9664\u3057\u305f\u5834\u5408\u306b\u30ec\u30b3\u30fc\u30c9\u306f\u81ea\u52d5\u524a\u9664\u3055\u308c\u308b<\/strong>
    \n    date = models.DateField()\n<\/div>\n<\/div>\n

    <\/div>\n

    on_delete\u306e\u30aa\u30d7\u30b7\u30e7\u30f3\u4e00\u89a7<\/h2>\n
      \n
    • on_delete\u30aa\u30d7\u30b7\u30e7\u30f3\u4e00\u89a7\u3068\u5404\u610f\u5473<\/li>\n<\/ul>\n\n\n\n\n\n\n\n\n\n\n
      \u30aa\u30d7\u30b7\u30e7\u30f3<\/th>\n\u610f\u5473<\/th>\n<\/tr>\n<\/thead>\n
      CASCADE<\/td>\nForeignKey\u306e\u5bfe\u8c61\u30ec\u30b3\u30fc\u30c9\u304c\u524a\u9664\u3055\u308c\u308b\u3068\u3001\u7d10\u3065\u3051\u5143\u306e\u30ec\u30b3\u30fc\u30c9\u304c\u5168\u3066\u524a\u9664\u3055\u308c\u308b<\/span><\/td>\n<\/tr>\n
      PROTECT<\/td>\nForeignKey\u306e\u5bfe\u8c61\u30ec\u30b3\u30fc\u30c9\u304c\u524a\u9664\u3057\u3088\u3046\u3068\u3057\u3066\u3082\u3001PrortectedError\u304c\u767a\u751f\u3057\u3066\u524a\u9664\u3055\u308c\u306a\u3044<\/span><\/td>\n<\/tr>\n
      SET_NULL<\/td>\nForeignKey\u306e\u5bfe\u8c61\u30ec\u30b3\u30fc\u30c9\u304c\u524a\u9664\u3055\u308c\u308b\u3068\u3001\u7d10\u3065\u3051\u5143\u306e\u30ec\u30b3\u30fc\u30c9\u306b\u306fnull<\/span>\u304c\u8a2d\u5b9a\u3055\u308c\u308b\u3002\u307e\u305f\u3053\u308c\u306f\u3001null=True<\/span>\u3068\u8a2d\u5b9a\u3057\u3066\u5229\u7528\u3057\u306a\u3051\u308c\u3070\u3044\u3051\u306a\u3044<\/td>\n<\/tr>\n
      SET_DEFAULT<\/td>\nForeignKey\u306e\u5bfe\u8c61\u30ec\u30b3\u30fc\u30c9\u304c\u524a\u9664\u3055\u308c\u308b\u3068\u3001ForeignKey\u306b\u306f\u30c7\u30d5\u30a9\u30eb\u30c8\u5024<\/span>\u304c\u8a2d\u5b9a\u3055\u308c\u308b\u3002\u307e\u305f\u3053\u308c\u306f\u3001\u30e2\u30c7\u30eb\u306bdefault=<\/span>\u3092\u8a2d\u5b9a\u3059\u308b\u5fc5\u8981\u304c\u3042\u308b<\/td>\n<\/tr>\n
      SET()<\/td>\nSET\u306e\u4e2d\u306b\u95a2\u6570\u3092\u8a2d\u5b9a\u3059\u308b\u3068\u3001\u524a\u9664\u306e\u969b\u306b\u8a2d\u5b9a\u3057\u305f\u95a2\u6570\u304c\u547c\u3073\u51fa\u3055\u308c\u308b<\/span><\/td>\n<\/tr>\n
      RESTRICT
      (Django3.1\u4ee5\u964d)<\/td>\n      		\u53c2\u7167\u5148\u3092\u524a\u9664\u3059\u308b\u969b\u306bRestictedError\u3092\u767a\u751f\u3055\u305b\u3066\u3001\u4fdd\u8b77\u3059\u308b\u3002\u305f\u3060\u3057\u3001\u53c2\u7167\u5148\u306e\u53c2\u7167\u5148\u304c\u524a\u9664\u3055\u308c\u308b\u969b\u306b\u3001CASCADE\u3067\u305d\u306e\u53c2\u7167\u5148\u306b\u7d10\u3065\u3051\u3089\u308c\u3044\u305f\u5834\u5408\u306b\u306f\u3001\u4fdd\u8b77\u3055\u308c\u305a\u524a\u9664\u3055\u308c\u308b\u3002<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      SET(), PROTECT, RESTRICT\u306e\u5177\u4f53\u7684\u306a\u5229\u7528\u65b9\u6cd5<\/h2>\n

      SET()\u3068PROTECT\u3068RESTRICT\u306e\u4ed5\u7d44\u307f\u306f\u308f\u304b\u308a\u306b\u304f\u3044\u306e\u3067\u3001\u4ee5\u4e0b\u306b\u5177\u4f53\u4f8b\u3092\u4e0a\u3052\u3066\u3054\u8aac\u660e\u3059\u308b\u3002<\/p>\n

      \n

      Example<\/h4>\n
        \n
      • SET()\u306e\u4e8b\u4f8b<\/li>\n<\/ul>\n
        \nfrom django.conf import settings
        \nfrom django.contrib.auth import get_user_model
        \nfrom django.db import models<\/p>\n

        def get_sentinel_user():# \u524a\u9664\u306b\u5b9f\u884c\u3055\u308c\u308b\u51e6\u7406\u3067return\u306e\u5024\u304c\u524a\u9664\u3055\u308c\u305f\u30ec\u30b3\u30fc\u30c9\u306b\u8a2d\u5b9a\u3055\u308c\u308b<\/strong>
        \n    return get_user_model().objects.get_or_create(username='deleted')[0]<\/p>\n

        class MyModel(models.Model):
        \n    user = models.ForeignKey(
        \n        settings.AUTH_USER_MODEL,
        \n        on_delete=models.SET<\/span>(get_sentinel_user), # models.SET\u3067\u524a\u9664\u6642\u306b\u5b9f\u884c\u3055\u308c\u308b\u95a2\u6570\u3092\u8a2d\u5b9a\u3059\u308b<\/strong>
        \n    )\n<\/div>\n

         
        \nRESTRICT\u3068PROTECT\u306f\u52d5\u4f5c\u304c\u4f3c\u3066\u3044\u308b\u305f\u3081\u3001\u4ee5\u4e0b\u306b\u56f3\u3092\u7528\u3044\u3066\u8aac\u660e\u3059\u308b\u3002<\/p>\n

          \n
        • RESTRICT\u3068PROTECT\u306e\u9055\u3044<\/li>\n<\/ul>\n

          \"\"<\/p>\n

            \n
          • RESTRICT\u306e\u4f8b<\/li>\n<\/ul>\n
            \nclass Students(models.Model):<\/p>\n

                name = models.CharField(max_length=20)
            \n    school = models.ForeignKey( # RESTRICT\u3092\u6307\u5b9a\u3059\u308b\u3002Schools\u524a\u9664\u6642\u306f\u30a8\u30e9\u30fc(RestictedError)<\/strong>
            \n        'Schools', on_delete=models.RESTRICT<\/span>
            \n    )
            \n    prefecture = models.ForeignKey( # CASCADE\u3092\u6307\u5b9a\u3059\u308b\u3002Schools\u524a\u9664\u6642\u306fSchools\u3068\u3068\u3082\u306b\u8a72\u5f53\u30ec\u30b3\u30fc\u30c9\u524a\u9664\u3055\u308c\u308b<\/strong>
            \n        'Prefectures', on_delete=models.CASCADE<\/span>
            \n    )<\/p>\n

            class Schools(models.Model):
            \n    name = models.CharField(max_length=20)
            \n    prefecture = models.ForeignKey( # CASCADE\u3092\u6307\u5b9a\u3059\u308b\u3002Schools\u524a\u9664\u6642\u306f\u8a72\u5f53\u30ec\u30b3\u30fc\u30c9\u524a\u9664\u3055\u308c\u308b<\/strong>
            \n        'Prefectures', on_delete=models.CASCADE<\/span>
            \n    )<\/p>\n

            class Prefectures(models.Model):
            \n    name = models.CharField(max_length=20)<\/p>\n<\/div>\n<\/div>\n

            <\/div>\n","protected":false},"excerpt":{"rendered":"

            Django2\u7cfb\u4ee5\u964d\u306emodels.py\u304b\u3089\u5fc5\u9808\u306b\u306a\u3063\u305fon_delete\u306b\u3064\u3044\u3066 Django\u3067\u306f\u30012.0\u4ee5\u964d\u306e\u30d0\u30fc\u30b8\u30e7\u30f3\u3067\u3001\u30e2\u30c7\u30eb\u3092\u4f5c\u6210\u3059\u308b\u969b\u306b\u3001on_delete\u3068\u3044\u3046\u30d1\u30e9\u30e1\u30fc\u30bf\u3092\u6307\u5b9a\u3059\u308b\u3053\u3068\u304c\u5fc5\u9808\u306b\u306a\u3063\u305f\u3002 on […]<\/p>\n","protected":false},"author":1,"featured_media":362,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_uag_custom_page_level_css":"","_uf_show_specific_survey":0,"_uf_disable_surveys":false,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[121,219],"tags":[122,130,131,14],"class_list":{"0":"post-700","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-django","8":"category-it-programming","9":"tag-django","10":"tag-model","11":"tag-on_delete","12":"tag-python","13":"entry"},"uagb_featured_image_src":{"full":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",640,480,false],"thumbnail":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480-150x150.jpg",150,150,true],"medium":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480-300x225.jpg",300,225,true],"medium_large":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",640,480,false],"large":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",640,480,false],"1536x1536":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",640,480,false],"2048x2048":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",640,480,false],"home-middle":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",467,350,false],"home-top":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",560,420,false],"sidebar-thumbnail":["https:\/\/www.nblog09.com\/w\/wp-content\/uploads\/2019\/01\/organization-2478211__480.jpg",100,75,false]},"uagb_author_info":{"display_name":"9nmatsumoto","author_link":"https:\/\/www.nblog09.com\/w\/author\/9nmatsumoto\/"},"uagb_comment_info":0,"uagb_excerpt":"Django2\u7cfb\u4ee5\u964d\u306emodels.py\u304b\u3089\u5fc5\u9808\u306b\u306a\u3063\u305fon_delete\u306b\u3064\u3044\u3066 Django\u3067\u306f\u30012.0\u4ee5…","_links":{"self":[{"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/posts\/700","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/comments?post=700"}],"version-history":[{"count":23,"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/posts\/700\/revisions"}],"predecessor-version":[{"id":3783,"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/posts\/700\/revisions\/3783"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/media\/362"}],"wp:attachment":[{"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/media?parent=700"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/categories?post=700"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.nblog09.com\/w\/wp-json\/wp\/v2\/tags?post=700"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}