Questions tagged [relationship]
Questions in this tag typically involve the association that a set of data has with other set(s) of data.
relationship
6,484
questions
436
votes
4
answers
554k
views
How to implement one-to-one, one-to-many and many-to-many relationships while designing tables?
Can anyone explain how to implement one-to-one, one-to-many and many-to-many relationships while designing tables with some examples?
- 23.9k
386
votes
2
answers
651k
views
Laravel - Eloquent "Has", "With", "WhereHas" - What do they mean?
I've found the concept and meaning behind these methods to be a little confusing, is it possible for somebody to explain to me what the difference between has and with is, in the context of an example ...
user4898812
164
votes
8
answers
345k
views
Laravel where on relationship object
I'm developing a web API with Laravel 5.0 but I'm not sure about a specific query I'm trying to build.
My classes are as follows:
class Event extends Model {
protected $table = 'events';
...
- 1,917
116
votes
9
answers
126k
views
Implementation difference between Aggregation and Composition in Java
I'm aware of the conceptual differences between Aggregation and Composition. Can someone tell me the implementation difference in Java between them with examples?
- 2,188
113
votes
6
answers
145k
views
Laravel save / update many to many relationship
Can anyone help me on how to save many to many relationship? I have tasks, user can have many tasks and task can have many users (many to many), What I want to achieve is that in update form admin can ...
- 1,306
109
votes
14
answers
102k
views
How to delete/create databases in Neo4j?
Is it possible to create/delete different databases in the graph database Neo4j like in MySQL? Or, at least, how to delete all nodes and relationships of an existing graph to get a clean setup for ...
- 3,225
102
votes
7
answers
133k
views
Delete all nodes and relationships in neo4j 1.8
I know this question is asked by many people already
for my research, here's some questions asked before
How to delete all relationships in neo4j graph?
https://groups.google.com/forum/#!topic/neo4j/...
- 2,265
100
votes
4
answers
161k
views
Laravel Eloquent - Attach vs Sync
What is the difference between attach() and sync() in Laravel 4's Eloquent ORM? I've tried to look around but couldn't find anything!
- 35.2k
97
votes
4
answers
165k
views
How to use an include with attributes with sequelize?
Any idea how to use an include with attributes (when you need to include only specific fields of the included table) with sequelize?
Currently I have this (but it doesn't work as expected):
var ...
- 11.5k
93
votes
6
answers
120k
views
UML relationships - dashed line vs solid line
What is the difference between these 2 relationships?
Edit: Also if you could provide a simple code example illustrating the difference, that would be really helpful!
- 6,193
79
votes
9
answers
259k
views
Meaning of "n:m" and "1:n" in database design
In database design what do n:m and 1:n mean?
Does it have anything to do with keys or relationships?
- 2,415
78
votes
11
answers
70k
views
SQLAlchemy cannot find a class name
Simplified, I have the following class structure (in a single file):
Base = declarative_base()
class Item(Base):
__tablename__ = 'item'
id = Column(BigInteger, primary_key=True)
# ... ...
- 46.8k
75
votes
4
answers
81k
views
Inserting new records with one-to-many relationship in sqlalchemy
I'm following the flask-sqlalchemy tutorial on declaring models regarding one-to-many relationship. The example code is as follows:
class Person(db.Model):
id = db.Column(db.Integer, primary_key=...
- 1,916
71
votes
7
answers
58k
views
How do I reload a relation collection in laravel?
In Laravel, after using attach() or detach() to add or remove something from a relation, the collection has not changed. So if I have a model whose relation contains [1, 2], after this:
$model->...
- 19.2k
65
votes
3
answers
27k
views
Understanding Core Data delete rules on One to Many
I am a little fuzzy about Core Data Relationships deletion rules. So if someone could help me answer a few questions about them.
I have Entities A and B. A has a to-Many relationship with B, and B ...
- 773
64
votes
2
answers
34k
views
anybody tried neo4j vs titan - pros and cons [closed]
Can anybody please provide or point out to a good comparison between Neo4j and Titan?
One thing i can see is in terms of scale - Titan is scaleout and requires an underlying scalable datastore like ...
- 1,221
60
votes
4
answers
30k
views
Ruby on rails - Reference the same model twice?
Is it possible to set up a double relationship in activerecord models via the generate scaffold command?
For example, if I had a User model and a PrivateMessage model, the private_messages table ...
- 703
60
votes
3
answers
121k
views
Laravel: Get pivot data for specific many to many relation
My User model has many Target and vice versa.
Now I've got a given User and given Target and I want to access pivot data from their relation. The pivot column is called type
How can I achieve this?
- 2,900
59
votes
3
answers
31k
views
Doctrine 2 - Disallow null value on foreign keys of ManyToOne relationships
I have a ManyToOne relationship in one of my entities, like so:
class License {
// ...
/**
* Customer who owns the license
*
* @var \ISE\LicenseManagerBundle\Entity\Customer
...
- 733
58
votes
2
answers
46k
views
What rel=profile is for?
While doing the HTML for my new template, I stumbled across a new meta tag
<link rel="profile" href="http://gmpg.org/xfn/11" />
What's this for? I found it linking to this page, and through ...
- 16k
51
votes
3
answers
36k
views
How do I access the properties of a many-to-many "through" table from a django template?
From the Django documentation...
When you're only dealing with simple many-to-many relationships such as mixing and matching pizzas and toppings, a standard ManyToManyField is all you need. However, ...
- 2,400
49
votes
9
answers
115k
views
How to find all the relations between all mysql tables?
How to find all the relations between all MySQL tables? If for example, I want to know the relation of tables in a database of having around 100 tables.
Is there anyway to know this?
- 491
42
votes
6
answers
87k
views
Laravel relationships in migrations?
I know you can define table relationships fairly easy with $this->belongs_to(), $this->has_many() etc, but what i don't understand is how the relationship table is created; the table that binds ...
- 5,246
40
votes
4
answers
25k
views
Laravel Polymorphic Relations Has Many Through
I have a Subscriber model
// Subscriber Model
id
user_id
subscribable_id
subscribable_type
public function user()
{
return $this->belongsTo('App\User');
}
public function subscribable()
{
...
- 431
40
votes
2
answers
23k
views
Neo4j Bidirectional Relationship
Is there a way to create bidirectional relationship in Neo4j using Cypher? I would like the relationship to be bidirectional rather than making two unidirectional relationships in both directions For ...
- 1,758
39
votes
7
answers
81k
views
Laravel check if relation is empty
I have an object with some relationships and I need to check if these relations are empty or not, I'm trying to check with is_null, isset, != undefined, etc but nothing works, here is the relationship ...
- 1,535
39
votes
1
answer
92k
views
Hibernate: Where do insertable = false, updatable = false belong in composite primary key constellations involving foreign keys?
When implementing composite primary keys in Hibernate or other ORMs there are up to three places where to put the insertable = false, updatable = false in composite primary key constellations that use ...
- 13.9k
39
votes
3
answers
92k
views
Determine Which Objects Reference a Table in SQL Server
I need to rename a table that has many columns and stored procedures that process against that table. How can one get all Items in database that have a relation to a table in such a scenario?
- 15.3k
38
votes
1
answer
29k
views
Elasticsearch relationship mappings (one to one and one to many)
In my elastic search server I have one index http://localhost:9200/blog.
The (blog) index contains multiple types.
e.g.: http://localhost:9200/blog/posts, http://localhost:9200/blog/tags.
In the ...
- 497
33
votes
4
answers
108k
views
Laravel whereDoesntHave() - multiple OR conditions
In Laravel 4.2 I have a model called Product with many-to-many relationshis to other models like Country or Category. I want to filter out products that are "incomplete", which means they have no ...
- 1,329
33
votes
1
answer
53k
views
Get ids array from related laravel model which is having belongsToMany relationship
I have a model Role which belongs to many Users.
Class Role {
public $fillable = ["name"];
public function users()
{
return $this->belongsToMany('App/Models/User')->...
- 333
33
votes
4
answers
25k
views
How to define two relationships to the same table in SQLAlchemy
I’ve looked all over the SQLAlchemy tutorial and other similar questions but I seem to be struggling to get this join to work:
The scenario: I have a pages table represented by the Page model. Pages ...
- 41.4k
33
votes
1
answer
57k
views
MySQL - How to insert into table that has many-to-many relationship
I have a table of persons. Each person has a property and many persons may have a certain property. So this is a many-to-many relationship. This is the schema:
CREATE TABLE persons (
person_id int(...
- 6,005
31
votes
3
answers
36k
views
How to view database diagram in a Code First using localdb
I have a Code First project with Entity Framework 5.0.0 using localdb created in Visual Studio 2012 Ultimate.
Although I can see my class relations in a Class Diagram, how to see a visual diagram of ...
- 30.6k
30
votes
5
answers
24k
views
Add record to a has_and_belongs_to_many relationship
I have two models, users and promotions. The idea is that a promotion can have many users, and a user can have many promotions.
class User < ActiveRecord::Base
has_and_belongs_to_many :...
- 457
29
votes
2
answers
14k
views
Laravel: Create morphs() relationship nullable
I want to create a one-to-one polymorphic relation allow null relation.
Example:
Schema::create('ps_assistances', function (Blueprint $table) {
$table->bigIncrements('id');
...
- 465
29
votes
6
answers
29k
views
Laravel merge relationships
Is there a way to merge 2 relationships in laravel?
this is the way it's setup now, but Is there a way I could return both merged?
public function CompetitionsHome() {
return $this->HasMany(...
- 2,743
28
votes
3
answers
45k
views
Can't get Laravel associate to work
I'm not quite sure if I understand the associate method in Laravel. I understand the idea, but I can't seem to get it to work.
With this (distilled) code:
class User
{
public function customer(...
- 3,224
27
votes
2
answers
10k
views
HABTM Polymorphic Relationship
I'm pretty new to Rails, and i'm trying to do a polymorphic HABTM relationship. The problem is that I have three models that I want to relate.
The first one is the Event model and then are two kind ...
- 870
27
votes
2
answers
10k
views
Many To Many relationships in Laravel: belongsToMany() vs. hasManyThrough()
What is the difference between using belongsToMany() or hasManyThrough() when defining a Many To Many relationship in Laravel?
Example:
User
Account
Account_User
So, User has a many to many relation ...
- 3,129
27
votes
2
answers
46k
views
SQLAlchemy: How to order query results (order_by) on a relationship's field?
Models
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, ForeignKey
from sqlalchemy import Integer
from sqlalchemy import Unicode
from sqlalchemy import TIMESTAMP
...
- 1,850
26
votes
3
answers
39k
views
Eloquent relations - attach (but don't save) to Has Many
I have the following relations set up:
class Page {
public function comments() {
return $this->hasMany('Comment');
}
}
class Comment {
public function page() {
return $...
- 15.8k
26
votes
5
answers
25k
views
MySQL Foreign Key On Delete
I am trying to figure out relationships and deletion options.
I have two tables, User and UserStaff, with a 1:n relationship from User to UserStaff (a user can have multiple staff members).
When my ...
- 5,024
26
votes
1
answer
8k
views
What inverse_of does mean in mongoid?
What inverse_of does mean in mongoid associations? What I can get by using it instead of just association without it?
- 14.7k
23
votes
7
answers
58k
views
Adding Relations to Laravel Factory Model
I'm trying to add a relation to a factory model to do some database seeding as follows - note I'm trying to add 2 posts to each user
public function run()
{
factory(App\User::class, 50)->create(...
- 9,978
23
votes
3
answers
9k
views
How to store bidirectional relationships in a RDBMS like MySQL?
Suppose I want to store relationships among the users of my application, similar to Facebook, per se.
That means if A is a friend(or some relation) of B, then B is also a friend of A. To store this ...
- 6,882
23
votes
1
answer
4k
views
How can I use ElasticSearch-Rails query dsl to return related relationships
I am new to ElasticSearch, but need to use it to return a list of products. Please do not include answers or links to old answers which reference the deprecated tire gem.
gemfile
ruby '2.2.0'
gem ...
- 2,446
22
votes
10
answers
73k
views
How to design a movie database?
I'm trying to get my head round this mind boggling stuff they call Database Design without much success, so I'll try to illustrate my problem with an example.
I am using MySQL and here is my question:...
- 26.4k
22
votes
6
answers
78k
views
Eloquent select rows with empty string or null value
I have something like $user->albums()->where('col', NULL), it works fine then I tried to extend it to empty strings with $user->albums()->where('col', NULL)->or_where('col', '') and it'...
- 9,788
22
votes
3
answers
55k
views
ER-Diagram: Ternary Relationship - How to read properly?
Im not quite sure how to read ternary relationships within a ER-Diagram.
Lets say this is the ternary relationship that is given.
What can I interpret out of that?
It says that you have to put your ...
- 405