relationship

How to store bidirectional relationships in a RDBMS like MySQL?

由 左心房为你撑大大i 提交于 2019-11-30 03:38:54
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 relationships I am currently planning to store them in a table for relations as follows UID FriendID ------ -------- user1 user2 user1 user3 user2 user1 However I am facing two options here: The typical case, where I will store both user1 -> user2 and user2->user1 . This will take more space, but (at least in my head) require just one pass over the rows to display the friends of a particular user.

REST api, POST entity with relationships?

由 喜你入骨 提交于 2019-11-30 03:13:49
问题 Im having an issue where I cant decide how to procced on this matter.. and I need to know if there is any standard way to solve this.. or if you guys have any great input for this matter. The thing is that I have started to build a very basic API for learning purpose The API is a simple Music store.. where the store has some Albums which requires and artist. So the Relationship is Artist <--- 1 ----- * ---> Albums and for an album to exist its required that that the album has an artist. But

UML Class diagram, how to show a Class extends thread?

由 安稳与你 提交于 2019-11-30 02:56:10
问题 I have a class called ServerSide in which another class resides called Cserver. The following code fragment should explain what I am talking about: public static void main (String [] args) throws Exception { System.out.println("The server is running."); int clientnumber = 1; ServerSocket server = new ServerSocket(9090); try { while (true) { new cserver(server.accept(), clientnumber++).start(); } }finally { server.close(); } } private static class cserver extends Thread { private Socket socket

Programming a one-to-many relationship

由 做~自己de王妃 提交于 2019-11-30 01:28:10
So I am surprised that doing a search on google and stackoverflow doesn't return more results. In OO programming (I'm using java), how do you correctly implement a one-to-many relationship? I have a class Customer and class Job . My application is for a fictious company that completes jobs for customers. My current implementation is so that the Job class doesn't have anything to do with the Customer class, there is no reference to it at all. The Customer class uses a collection and methods to hold, retrieve and modify information about the Jobs that have been assigned by and/or completed for a

How to specify Parent-Child relationship within one Model?

由 喜你入骨 提交于 2019-11-29 23:55:29
问题 For example I have following code: class FamilyMember(models.Model): user = models.OneToOneField(User) And I have following situations: a1 = FamilyMember.objects.get(id=1) a1.first_name = 'John' a1.last_name = 'Smith' (a1 is a parent of a2) a2 = FamilyMember.objects.get(id=2) a2.first_name = 'Mark' a2.last_name = 'Smith' (a2 is a child of a1 and parent of a3 in the same time) a3 = FamilyMember.objects.get(id=3) a3.first_name = 'Jason' a3.last_name = 'Smith' (a3 is a child of a2) How can i

EF6 Code First - may cause cycles or multiple cascade paths

由 别来无恙 提交于 2019-11-29 19:42:06
问题 I'm using EF6 Code First. I have two classes: public class Player { [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)] [Key] public int Id { get; set; } [Required, MinLength(2, ErrorMessage = "Player name must be at least 2 characters length")] public string Name { get; set; } [Required] public int TeamClubId { get; set; } [Required] public int TeamNationalId { get; set; } [Required, ForeignKey("TeamClubId")] public virtual Team Club { get; set; } [Required, ForeignKey(

Neo4jClient - Retrieving relationship from Cypher query

由 别说谁变了你拦得住时间么 提交于 2019-11-29 16:56:42
I'm having trouble retrieving matched relationships from a Cypher query. I have this simple trial code: var movie = client.Create(new Movie { Title = "The Matrix" }); client.Create(new Actor { Name = "Keanu Reeves" }, new ActedIn(movie, new ActedInPayload { Role = "Neo" })); client.Create(new Actor { Name = "Hugo Weaving" }, new ActedIn(movie, new ActedInPayload { Role = "Agent Smith" })); var actorsAndRoles = client .Cypher .Start(new { movie = movie }) .Match("actor-[r:ACTED_IN]->movie") .Return((actor, r) => new { Actor = actor.As<Node<Actor>>() // ActedIn = r.As<?????>() }) .Results;

Can't get Laravel associate to work

由 天涯浪子 提交于 2019-11-29 16:23:04
问题 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() { return $this->hasOne('Customer'); } } class Customer { public function user() { return $this->belongsTo('User'); } } $user = new User($data); $customer = new Customer($customerData); $user->customer()->associate($customer); I get a Call to undefined method Illuminate\Database\Query\Builder:

Laravel: how to get average on nested hasMany relationships (hasManyThrough)

由 别说谁变了你拦得住时间么 提交于 2019-11-29 14:30:39
问题 I have three tables: products: id|name|description|slug|category_id|... reviews: id|product_id|review_text|name|email|... review_rows id|review_id|criteria|rating the review table stores the review text, writer of the review and has a foreign product_id key. The review_rows table stores the ratings for different criteria like: ---------------------------------------- | id | criteria | rating | review_id | ---------------------------------------- | 1 | price | 9 | 12 | ------------------------

How to speed up updating relationship among tables, after one or both tables are already saved?

由 微笑、不失礼 提交于 2019-11-29 13:54:01
Question: Update and save fast, relationship between tables with lots of data after both or one of the table is already saved. I have five tables TvGenres, TvSubgenre, TvProgram, Channels, TvSchedules with the relationship between them as shown in below image Now the problem is all data downloading happens in sequence based on previous data and unlike SQLite, I need to set relationship between them and to do that I have to search table again and again and set the relation between them which is time-consuming so how can I do that faster I use 2 different approaches to solve but both are not
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