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Questions tagged [one-to-many]

one-to-many is relationship between two different object properties.

One object property is relating with many properties of other object. Or you can say one object relating to many objects.

In sql, a one-to-many relationship, each row in the related to table can be related to many rows in the relating table.

http://en.wikipedia.org/wiki/One-to-many

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Hibernate throws MultipleBagFetchException - cannot simultaneously fetch multiple bags

Hibernate throws this exception during SessionFactory creation: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags This is my test case: Parent.java @Entity public Parent { @Id …
blow
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What is the meaning of the CascadeType.ALL for a @ManyToOne JPA association

I think I misunderstood the meaning of cascading in the context of a @ManyToOne relationship. The case: public class User { @OneToMany(fetch = FetchType.EAGER) protected Set
userAddresses; } public class Address { …
forhas
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How to express a One-To-Many relationship in Django?

I'm defining my Django models right now and I realized that there wasn't a OneToManyField in the model field types. I'm sure there's a way to do this, so I'm not sure what I'm missing. I essentially have something like this: class…
Naftuli Kay
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Difference Between One-to-Many, Many-to-One and Many-to-Many?

Ok so this is probably a trivial question but I'm having trouble visualizing and understanding the differences and when to use each. I'm also a little unclear as to how concepts like uni-directional and bi-directional mappings affect the…
Ian Dallas
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What is “the inverse side of the association” in a bidirectional JPA OneToMany/ManyToOne association?

In the example section of the @OneToMany JPA annotation reference: Example 1-59 @OneToMany - Customer Class With Generics @Entity public class Customer implements Serializable { ... @OneToMany(cascade=ALL, mappedBy="customer") public…
Behrang
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Difference between one-to-many and many-to-one relationship

What is the real difference between one-to-many and many-to-one relationship? It is only reversed, kind of? I can't find any 'good-and-easy-to-understand' tutorial about this topic other than this one: SQL for Beginners: Part 3 - Database…
Zhaf
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JPA: How to have one-to-many relation of the same Entity type

There's an Entity Class "A". Class A might have children of the same type "A". Also "A" should hold it's parent if it is a child. Is this possible? If so how should I map the relations in the Entity class? ["A" has an id column.]
sanjayav
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Hibernate OneToMany java.lang.StackOverflowError

It's my first question here on stack, so please be gentle :D I'm trying to create hibernate OneToMany relationship. When I try to fetch some data from my DB, I'm getting StackOverflowError. But when i remove OneToMany part, everything goes normally.…
otocon
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JPA - Persisting a One to Many relationship

Maybe this is a stupid question but it's bugging me. I have a bi-directional one to many relationship of Employee to Vehicles. When I persist an Employee in the database for the first time (i.e. it has no assigned ID) I also want its associated…
JMM
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Doctrine 2 OneToMany Cascade SET NULL

The error Cannot delete or update a parent row: a foreign key constraint fails. The classes class Teacher { /** *@ORM\OneToMany(targetEntity="publication", mappedBy="teacher") */ protected $publications; } class Publication { …
Nicolas Lino
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Hibernate/JPA ManyToOne vs OneToMany

I am reading currently the documentation of Hibernate regarding the entity associations and I come accross a little difficulty to figure out some things. It has to do in essence with the difference between ManyToOne and OneToMany associations.…
arjacsoh
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AttributeError: 'int' object has no attribute '_sa_instance_state'

I'm working on forum template using Flask. When I attempt creating a new thread in the browser using forms, SQLAlchemy throws an AttributeError. The problem showed up when I tried implementing a one-to-many relationship with Forum-to-Thread and a…
Ganye
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When to use inverse=false on NHibernate / Hibernate OneToMany relationships?

I have been trying to get to grips with Hibernate's inverse attribute, and it seems to be just one of those things that is conceptually difficult. The gist that I get is that when you have a parent entity (e.g. Parent) that has a collection of…
James Allen
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Deleted object would be re-saved by cascade (remove deleted object from associations)

I have the following two entities: 1- PlayList: @OneToMany(fetch = FetchType.EAGER, mappedBy = "playlist", orphanRemoval = true, cascade = CascadeType.ALL) @OrderBy("adOrder") private Set PlaylistadMaps = new…
Mahmoud Saleh
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One-To-Many relationship gets duplicate objects without using "distinct". Why?

I have 2 classes in a one-to-many relationship and a HQL query that is a bit strange. Even if I have read some questions already posted, it does not seem clear to me. Class Department{ @OneToMany(fetch=FetchType.EAGER, mappedBy="department") …
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