Cascade

class Owner { static hasMany = Dog } class Sitter { static hasMany = Dog } class Dog { static belongsTo = [Owner, Sitter] } My question is: If I create a Dog instance D, a Owner instance O, a Sitter instance S and associate D with both O and S, what happens to O when S gets deleted? Would O still have D? Since it's a cascade-delete, both S and D would get deleted, right? When what happens to O? Would it still have D? I have tested it, it follows the cascade rule: if you delete Owner, Dog will be deleted by cascade, but Sitter will remain. And it's reasonable: Sitter is independent with Owner.

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CASCADE ：父表delete、update的时候，子表会delete、update掉关联记录； SET NULL ：父表delete、update的时候，子表会将关联记录的外键字段所在列设为null，所以注意在设计子表时外键不能设为not null； RESTRICT ：如果想要删除父表的记录时，而在子表中有关联该父表的记录，则不允许删除父表中的记录； NO ACTION ：同 RESTRICT，也是首先先检查外键； 来源： https://my.oschina.net/depeng414/blog/3133606

Is there a way to merge two primary keys into one and then cascade update all affected relationships? Here's the scenario: Customers (idCustomer int PK, Company varchar(50), etc) CustomerContacts (idCustomerContact int PK, idCustomer int FK, Name varchar(50), etc) CustomerNotes (idCustomerNote int PK, idCustomer int FK, Note Text, etc) Sometimes customers need to be merged into one. For example, you have a customer with the id of 1 and another with the id of 2. You want to merge both, so that everything that was 2 is now 1. I know I could write a script that updates all affected tables one by

I created table with FOREIGN KEY and can't insert anything. CREATE TABLE menus ( id int(10), parent_id int(10), label varchar(255), PRIMARY KEY (id), FOREIGN KEY (parent_id) REFERENCES menus (id) ); I need FOREIGN KEY to automatically delete children when parent was deleted. This table was successfully created but I can't insert anything. INSERT INTO `menus` (`parent_id`, `label`) VALUES ('1', 'label1'); or INSERT INTO `menus` (`label`) VALUES ( 'label1'); #1452 - Cannot add or update a child row: a foreign key constraint fails I really don't want look for any children in php code so I need

I have a set hibernate.hbm2ddl.auto to create so that Hibernate creates the tables in mysql for me. However, it doesn't seem that hibernate correctly adds Cascade on the references in the table. It does however work when I for instance delete a row, and I have a delete cascade as hibernate annotation . So I guess that means that Hibernate reads the annoation on runtime, and perform cascading manually? Is that normal behavior? For instance: @Entity class Report { @OneToOne(cascade = CascadeType.ALL) public File getPdf() { return pdf; } } Here I have set cascade to ALL. However, when running