A delete operation could remove a record from a parent table, leaving records in an associated child table that no longer have a matching record in the parent table.

一个删除操作可以从一个父表中删除一条记录，使得相关子表中的记录在父表中没有与之匹配的记录。

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ON DELETE CASCADE—When a record is deleted from the parent table, all records in the child table with matching foreign key values are also deleted.

ON DELETE CASCADE — 当一条记录从父表中删除时，子表中的所有记录以及匹配的外键值都全部被删除。

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Internally to the library, all DataObjects in a graph are referenced by their parent and are maintained until detached from the data graph, so you don't need to delete DataObjects.

在该库内部，图中的所有数据对象都由其父项引用，并将保持到从数据图断开为止，因此并不需要删除数据对象。

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