Cascade

数据库里的cascade的用法，Mysql和Hibernate里面是不相同。 在数据库里，进行增加、修改、删除记录的时候，经常会涉及到父子关系的表。 例如：有省份表和城市表，其中城市表有一个外键province_id引用到省份表的主键。这样，可以把省份表看成是父表，把城市表看成是子表，城市表记录的存在依赖于省份表的记录。（文中提到的例子，所有的代码在附件里都有，所以这里的描述从简） 一、在MySQL里的cascade 以下直接在MySQL的控制台操作省份表和城市表 在省份表增加一条“广东”的记录，在城市表增加一条“广州”的记录，并且把“广州”的外键引用到“广东”的主键。“广州”的存在依赖于“广东”，如果删除省份表的“广东”，将会影响到城市表的“广州”。根据城市表的外键约束的on delete设置，有如下三种情况： 1、外键没有on delete的设置：当删除“广东”的时候，MySQL会报错，删除失败。 2、外键设置为on delete cascade：当删除“广东”的时候，同时把“广州”也删除。 3、外键设置为on delete set null：当删除“广东”的时候，“广州”的外键province_id会被自动设置为null，即“广州”脱离了对“广东”的依赖关系。 二、在Hibernate里的cascade 以下用Hibernate来操作省份表和城市表 首先，在hibernate

What does Cascade in Nhibernate mean? I see a lot of options in cascading: Delete All AllDeleteOrphan DeleteOrphan SaveUpdate Can you explain these with with examples and their distinctions? Mitch Wheat It means apply the action to an item's related items. Please see: NHibernate Cascades: the different between all, all-delete-orphans and save-update : none - do not do any cascades, let users handle them by themselves. save-update - when the object is saved/updated, check the associations and save/update any object that requires it (including save/update the associations in many-to-many

I implemented a bidirectional 1:1 relationship based on this answer: Primary /Foreign Key in Entity Framework I define the bidirectional relation this way: public class Student { public virtual int StudentId { get; set; } public virtual Anamnesis Anamnesis { get; set; } . . . } public class Anamnesis { [Key, ForeignKey("Student")] public int AnamnesisId { get; set; } public virtual Student Student { get; set; } . . . } where, Student is the principal entity and Anamnesis it the entity that shares the PK. Now I'd like that the relationship created had a Delete Rule = CASCADE. Actually, the

What's the difference in a MySQL FK between RESTRICT and NO ACTION ? From the doc they seem exactly the same. Is this the case? If so, why have both? From MySQL Documentation: https://dev.mysql.com/doc/refman/8.0/en/create-table-foreign-keys.html Some database systems have deferred checks, and NO ACTION is a deferred check. In MySQL, foreign key constraints are checked immediately, so NO ACTION is the same as RESTRICT . They are identical in MySQL. In the SQL 2003 standard there are 5 different referential actions: CASCADE RESTRICT NO ACTION SET NULL SET DEFAULT The difference between NO

I have two classes A and B. Many B's can have association with a single A, hence a many-to-one relationship from B to A. I've mapped the relationship like: <class name="A" table="tbl_A"> <property name="propA" column="colA"/> </class> <class name="B" table="tbl_B"> <property name="propB" column="colB"/> <many-to-one name="a" class="A" column="col1" cascade="delete"/> </class> A has nothing mapped to B. Keeping this in mind we intend to delete B when it's associated A is deleted. This could have been possible if I could define an inverse="true" on the many-to-one association in B but hibernate

I'm getting this error when submitting the form: org.hibernate.PersistentObjectException: detached entity passed to persist: com.project.pmet.model.Account; nested exception is javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: com.project.pmet.model.Account Here are my entities: Account: @Entity @DynamicInsert @DynamicUpdate public class Account { @Id @GeneratedValue private Integer id; @Column(nullable = false) private String login; @Column(nullable = false) private String password; @Column(nullable = false) private String