Questions tagged [many-to-one]
1040 questions
6
votes
2 answers
Django model relationship to multiple models
Suppose there is an abstract model CarOwner: whereas a Person or a Business can be a CarOwner. In addition a Car with a certain VIN can belong (relate) to either a Person or a Business, but not both (mutually exclusive case). At the very end of the…
jazzblue
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6
votes
2 answers
Symfony ManyToOne relationship getter returns empty object
I'll simplifly my code, I have te next:
Doctor entity:
use ...\...\Entity\Paciente;
class Doctor extends Usuario {
public function __construct() {
...
$this->pacientes = new ArrayCollection();
…
MSánchez
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5
votes
2 answers
many to one mapping Hash Function
I don't know the actual mathematical term (many to one mapping is the terminology i've used)
This is my requirement:
hash_code = hash_function(element 1, element 2, ...... element n)
i should be able to retrieve
bool b = is_valid_hash(hash_code,…
PC.
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5
votes
1 answer
How to prevent unnecessary select on insert?
I have the following scenario (in Java / Hibernate):
I have two entity classes: X and Y. X has a @ManyToOne association to Y which is not cascaded.
I create an (unmanaged) instance x of X and an (unmanaged) instance y of Y, and fill the reference…
Rubrick
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5
votes
0 answers
Play 2.6 Ebeans relationship error
Posts Model
/*set many to one relation with Privacy_Level model*/
@ManyToOne//(fetch = FetchType.LAZY)
@JoinColumn(name = "privacy_level_id",referencedColumnName = "id", insertable = false, updatable = false)
public Privacy_Level…
CraZyDroiD
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5
votes
2 answers
NHibernate with mapping by code and a SQLite database: saving many-to-one parent-child entities, child gets a null foreign key
Variations of this question have been asked and answered many times and the answers have a lot of overlapping details. I have tried so many different things suggested by these answers, but none of them have worked in my case.
I have a SQLite…
rory.ap
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5
votes
2 answers
Disable Cascade in ManyToOne relationship JPA when saving
I'm having problems when saving entities in my DB.
I have something like (very simplified) :
@Entity
public class Building {
@OneToMany(mappedBy = "building", fetch = FetchType.EAGER)
private List employees;
}
@Entity
public…
jpadilladev
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5
votes
2 answers
Hibernate @Filter on @ManyToOne
Could some please explain me why Having a @Filter on a @ManyToOne relation does not work?
Here i have a really simple example showing this:
I have created two simple table in my database (foo and bar)
Foo: id/id_bar
bar: id/name/state (state can be…
Johny19
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5
votes
2 answers
JPA unidirectional @OneToOne vs @ManyToOne with Hibernate - no difference?
According to book Pro JPA 2 the main difference between unidirectional @ManyToOne and @OneToOne is that in @OneToOne:
Only one instance of the source entity can refer to the same target entity instance.
In other words, the target entity instance…
user1071076
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5
votes
3 answers
Many-to-one relation returns None object: SqlAlchemy
I'm trying to write Schedule class which contains records like this:
... session, base, engine declaration somewhere here...
class Schedule(Base):
__tablename__ = 'schedule'
id = Column(Integer, primary_key=True)
# and here i need ref to…
Mikhail Elizarev
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5
votes
9 answers
org.hibernate.InvalidMappingException: Could not parse mapping document from resource *.hbm.xml
I know this question has been asked a lot, but I read almost every one of them but non of them helped me.
I'm writing an eclipse maven project with hibernate and I'm getting this error:
org.hibernate.InvalidMappingException: Could not parse mapping…
Raein Hashemi
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5
votes
2 answers
Does Hibernate always load associated object even if it can be null?
I have a question regarding Hibernate.
I have two objects with a Many-to-One relationship:
Eg:
Object 1:
public class Person {
@Basic
@Column(length = 50)
protected String name;
@NotFound(action=NotFoundAction.IGNORE)
@ManyToOne(fetch =…
rioubenson
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5
votes
1 answer
M:N relationship in JPA (wrapping given tables)
I have a m:n relationship book - borrow - user, the borrow is the join table.
The tables are given (can not be changed):
on one side they are used by jdbc app as well.
on the other side i would like to use them via jpa
book(book_id) -…
cscsaba
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4
votes
2 answers
Null foreign key, in ManyToOne relation using hibernate [4.1.1] annotations
I am trying to persist a one-to-many and a many-to-one relation using Hibernate 4.1.1 but the foreign key is always NULL.
There are two entities: Account and Client. A Client could have multiple Accounts while an Account has exactly one Client.
Here…
Laurențiu Onac
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4
votes
1 answer
A lookup table for one-to-many relationship?
I understand that a lookup table is necessary when we are dealing with many-to-many relationship.
But what about one-to-many relationship - do we need a lookup table or a foreign key in one of the tables?
Another question, is one-to-many the same as…
Run
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