relationship

问题 This question already has an answer here : Entity Framework Core many-to-many navigation issues (1 answer) Closed 10 months ago . as you know we don't have automatic Many to Many Relations between Entities in EF Core. whats the best solution to achieve that? here what I create for do that: class Student { public int StudentId { get; set; } public string Name { get; set; } public string Family { get; set; } public List<StudentCourse> Courses { get; set; } } class Course { public int CourseId {

问题 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=True) name = db.Column(db.String(50)) addresses = db.relationship('Address', backref='person', lazy='dynamic') class Address(db.Model): id = db.Column(db.Integer, primary_key=True) email = db.Column(db.String(50)) person_id = db.Column(db.Integer, db.ForeignKey('person.id')) Now I'm wondering how to

问题 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=True) name = db.Column(db.String(50)) addresses = db.relationship('Address', backref='person', lazy='dynamic') class Address(db.Model): id = db.Column(db.Integer, primary_key=True) email = db.Column(db.String(50)) person_id = db.Column(db.Integer, db.ForeignKey('person.id')) Now I'm wondering how to

问题 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=True) name = db.Column(db.String(50)) addresses = db.relationship('Address', backref='person', lazy='dynamic') class Address(db.Model): id = db.Column(db.Integer, primary_key=True) email = db.Column(db.String(50)) person_id = db.Column(db.Integer, db.ForeignKey('person.id')) Now I'm wondering how to

问题 How would I run a subquery on withCount()? I have a query I want to run for multiple counts, each with their own subqueries. Here is an example of something that I'm looking for: $date_from = Carbon::parse('1/1/2018'); $date_to = Carbon::parse('1/2/2018'); $models = Model::query() ->withCount('relation1', function (Builder $query) use ($date_from, $date_to) { $query->whereBetween('relation1.date1', [$date_from, $date_to]) ->where('value1', true); }) ->withCount('relation2', function (Builder

问题 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's not working. Also I saw on this post that I could use where_null('col') but it's not working and it's not documented. Any simple method to select where empty or NULL col 回答1: Try using orWhereNull for the second clause: $users = DB::table('users') ->where('col', '=', '') ->orWhereNull('col') ->get(); 回答2:

问题 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's not working. Also I saw on this post that I could use where_null('col') but it's not working and it's not documented. Any simple method to select where empty or NULL col 回答1: Try using orWhereNull for the second clause: $users = DB::table('users') ->where('col', '=', '') ->orWhereNull('col') ->get(); 回答2:

问题 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's not working. Also I saw on this post that I could use where_null('col') but it's not working and it's not documented. Any simple method to select where empty or NULL col 回答1: Try using orWhereNull for the second clause: $users = DB::table('users') ->where('col', '=', '') ->orWhereNull('col') ->get(); 回答2:

问题 I have a SwiftUI project with Core Data. The data model is a simple one-to-many and two primary views which each have a textfield at the top and a button to add a new item to the list view below. The first view is for the One side of the relation and the second for the Many. So, the NavigationLink in the first opens the second and passes the One object. Pretty standard stuff, it would seem. The methodology for creating the One works and the list below gets updated immediately when the managed

问题 I have a SwiftUI project with Core Data. The data model is a simple one-to-many and two primary views which each have a textfield at the top and a button to add a new item to the list view below. The first view is for the One side of the relation and the second for the Many. So, the NavigationLink in the first opens the second and passes the One object. Pretty standard stuff, it would seem. The methodology for creating the One works and the list below gets updated immediately when the managed