relationship

问题 I have two data structures "database" and "components" const DatabaseSchema = mongoose.Schema({ components: [{ type: Schema.Types.ObjectId, ref: 'Components', required: false }], }); const ComponentsSchema = mongoose.Schema({ name: { type: String, required: true, trim: true, unique: true, lowercase: true }, updatedAt: Date, }); I want to filter all items in the database by component names search rule I'm using Database.find({ components: { $elemMatch: { name: /antr/i } } }).populate({ path:

问题 I would like to establish a many-to-many relationship with a constraint that only one or no entity from each side of the relationship can be linked at any one time. A good analogy to the problem is cars and parking garage spaces. There are many cars and many spaces. A space can contain one car or be empty; a car can only be in one space at a time, or no space (not parked). We have a Cars table and a Spaces table (and possibly a linking table). Each row in the cars table represents a unique

问题 I am working in a project with scala play 2 framework where i am using slick as FRM and postgres database. In my project customer is an entity. So i create a customer table and customer case class and object also. Another entity is account. The code is given bellow case class Customer(id: Option[Int], status: String, balance: Double, payable: Double, created: Option[Instant], updated: Option[Instant]) extends GenericEntity { def this(status: String, balance: Double, payable: Double) = this

问题 Why would I create a recursive relationship? aField = models.ForeignKey('self') Is this the same with the above? class aClass(models.Model): aField = models.ForeignKey('aClass') 回答1: You may need to create a recursive relationship when you would like to have parent and child nodes with identical model structure. For example if you have comments with text, data and user_id: class Comment( models.Model ): text = models.TextField() create_date_time = models.DateTimeField() parent_comment =

问题 Table name: Author AuthorID -> primary key FirstName LastName Table name: Titles ISBN -> primary key BookTitle EditionNumber CopyRight Table name: AuthorISBN ISBN -> foreign key AuthorID -> foreign key How come the below code block below does not trigger the intellisense, since Linq-to-SQL automatically creates properties based on foreign-key relationship? In my case it doesn't... ERROR: The name title does not exist in current context in title.AuthorISBN It's not letting me add a photo, but

问题 what kind of relation (1:1, 1:m, m:m, whatever) there is between this two tables? CREATE TABLE IF NOT EXISTS `my_product` ( `id` int(11) NOT NULL auto_increment, `price` float default NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ; CREATE TABLE IF NOT EXISTS `my_product_i18n` ( `id` int(11) NOT NULL, `culture` varchar(7) NOT NULL, `name` varchar(50) default NULL, PRIMARY KEY (`id`,`culture`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; ALTER TABLE `my_product

问题 I have a small REST API that is being consumed by a single page web application powered by Backbone.js There are two resource types that the API provides, and therefore, the Backbone app uses. These are articles and comments. These two resources have different endpoints and there is a link from each of the articles to the location of all the comments for that item. The problem that I'm facing is that, on the article list in my web app I would like to be able to display the number of comments

问题 i'm trying to relate two entities with JPA, when i run the project don't throws me errors but when i request the method that get me the Voters of a Comunity Leader i get the next Exception: java.lang.StackOverflowError: null at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:245) ~[gson-2.8.5.jar:na] at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69) ~[gson-2.8.5.jar:na] at com

问题 Normally I have no issue with MySQL's PHPmyadmin designer to create referential integrity relations. All of a sudden, I now get a 99% Loading in my browser window, and a popup php. Reproduce; Select a database. Select designer. Select 'Set Relation' Select a primary key Select a coresponding foriegn key Approve confirmation Expected results; (and what I usually get) A relationship is setup. A line connecting two keys. Actual results; a green label "Loading 99%" appears in upper right corner.

问题 I'm relatively new to Laravel and have been working on it in my internship for the last 3 weeks however now I have a problem. I have 3 tables: Users, Bids, and Jobs. I want a user to be able to place a bid on the job. The basic structure of my tables is as follows: Users: id | name | email | description Jobs: id | title | description Bids: id | proposal The following criteria need to be met: A user can bid on many jobs, however they can only bid on each job once. A job can have many bids from