I want to know about relation dependent destroy and dependent nullify on rails and relation with SQL.
我想知道在rails上依赖关系的销毁和依赖关系的无效，以及与SQL的关系。
Thanks
谢谢
3 个解决方案
#1
2
Example: Table users and table cars
例如:桌面用户和桌面车
user has many cars car belongs to users
用户拥有许多属于用户的汽车
in table car you have user_id on each row
在表car中，每一行都有user_id
if you set dependent destroy when defining the relationship in users, then when you delete a user, all cars having that user_id will be deleted also
如果在定义用户关系时设置了依赖销毁，那么在删除用户时，所有具有user_id的汽车也将被删除
if you set nullify, cars will remain, but the user_id column will be set to null (it is pointless to have any value there because the user with that id was deleted)
如果设置为nullify, cars将保持不变，但user_id列将被设置为null(没有任何值是没有意义的，因为具有该id的用户已被删除)
Hope that this helps
希望这对您有所帮助
#2
0
You use these options when you want to get rid of orphaned records. Most common used is destroy because it removes all associated objects one by one.
当您想要删除孤立的记录时，您可以使用这些选项。最常见的用法是销毁，因为它逐个删除所有关联的对象。
#3
0
You can use dependent when we want to get rid of orphaned records since they can lead to various problems. Orphaned records are created when we delete or destroy a model A that was associated with model B, but model B wasn't removed in the process.
当我们想要删除孤立的记录时，您可以使用dependency，因为它们可能导致各种各样的问题。当我们删除或销毁与模型B关联的模型a时，会创建孤立的记录，但过程中并没有删除模型B。
You most often want to use destroy - all associated objects will remove one by one. other common options are:
您通常希望使用destroy——所有关联的对象将逐个删除。其他常见的选项是:
:delete_all – all associated objects will be deleted in a single query.
:delete_all -所有关联对象将在一个查询中被删除。
:nullify – foreign keys will be set to NULL
:nullify -外键将被设置为NULL
You can check more details about this here.
你可以在这里查看更多细节。
#1
2
Example: Table users and table cars
例如:桌面用户和桌面车
user has many cars car belongs to users
用户拥有许多属于用户的汽车
in table car you have user_id on each row
在表car中，每一行都有user_id
if you set dependent destroy when defining the relationship in users, then when you delete a user, all cars having that user_id will be deleted also
如果在定义用户关系时设置了依赖销毁，那么在删除用户时，所有具有user_id的汽车也将被删除
if you set nullify, cars will remain, but the user_id column will be set to null (it is pointless to have any value there because the user with that id was deleted)
如果设置为nullify, cars将保持不变，但user_id列将被设置为null(没有任何值是没有意义的，因为具有该id的用户已被删除)
Hope that this helps
希望这对您有所帮助
#2
0
You use these options when you want to get rid of orphaned records. Most common used is destroy because it removes all associated objects one by one.
当您想要删除孤立的记录时，您可以使用这些选项。最常见的用法是销毁，因为它逐个删除所有关联的对象。
#3
0
You can use dependent when we want to get rid of orphaned records since they can lead to various problems. Orphaned records are created when we delete or destroy a model A that was associated with model B, but model B wasn't removed in the process.
当我们想要删除孤立的记录时，您可以使用dependency，因为它们可能导致各种各样的问题。当我们删除或销毁与模型B关联的模型a时，会创建孤立的记录，但过程中并没有删除模型B。
You most often want to use destroy - all associated objects will remove one by one. other common options are:
您通常希望使用destroy——所有关联的对象将逐个删除。其他常见的选项是:
:delete_all – all associated objects will be deleted in a single query.
:delete_all -所有关联对象将在一个查询中被删除。
:nullify – foreign keys will be set to NULL
:nullify -外键将被设置为NULL
You can check more details about this here.
你可以在这里查看更多细节。