sqlite

问题 I'm using Django 3.0.6 I'm adding ForeignKey and ManyToManyField to my models, but I've noticed that django creates the INDEX , but not the actual FOREIGN KEY constraints in the db. I've tried to explicitly set db_constraint=True but as expected is useless, since it's True by default. I've found so many answers explaining this, but only for very old Django versions, doing tricks for enabling it when it was otherwise disabled. Now instead it should just work out of the box. Couldn't find

问题 model.py from django.db import models from django.utils import timezone Create your models here. class PageOnHold(models.Model): timestamp = models.DateTimeField(max_length=None,blank=True, null=True,default=timezone.now) spent_time = models.IntegerField(max_length=None,blank=True, null=True) elapsed_time = models.DateTimeField(max_length=None,blank=True, null=True,default=timezone.now) class MouseClick(models.Model): timestamp = models.DateTimeField(blank=True, null=True,default=timezone.now

问题 model.py from django.db import models from django.utils import timezone Create your models here. class PageOnHold(models.Model): timestamp = models.DateTimeField(max_length=None,blank=True, null=True,default=timezone.now) spent_time = models.IntegerField(max_length=None,blank=True, null=True) elapsed_time = models.DateTimeField(max_length=None,blank=True, null=True,default=timezone.now) class MouseClick(models.Model): timestamp = models.DateTimeField(blank=True, null=True,default=timezone.now

问题 I have an sqlite database from which I read data. I also have a long widget tree. So after a bit of research I found the provider Flutter package. But I can't figure out how to use Futures inside the class extending ChangeNotifier or How to use it anywhere in my widget tree? class MyProvider with ChangeNotifier { dynamic _myValue; dynamic get myValue => _myValue; set myValue(dynamic newValue) { _myValue = newValue; notifyListeners(); } MyProvider(){ loadValue(); } Future<void> loadValue async

问题 I have an sqlite database from which I read data. I also have a long widget tree. So after a bit of research I found the provider Flutter package. But I can't figure out how to use Futures inside the class extending ChangeNotifier or How to use it anywhere in my widget tree? class MyProvider with ChangeNotifier { dynamic _myValue; dynamic get myValue => _myValue; set myValue(dynamic newValue) { _myValue = newValue; notifyListeners(); } MyProvider(){ loadValue(); } Future<void> loadValue async

问题 I have a Flutter/Dart application that I am coding using Android Studio. I use a database called envirodatabase.db with the sqflite package. I want to open the database in DB Browser for SQLite on my computer, but the only way it lets me do that is through saving a copy of the file, not the file itself. How do I open the original file in DB Browser for SQLite? Here is my Device File Explorer What I tried doing was I right clicked > Save As in the Device File Explorer where my app's database

问题 I'm studying Laravel and working around in php artisan but I keep on getting this error: Illuminate/Database/QueryException with message 'SQLSTATE[23000]: Integrity constraint violation: 19 NOT NULL constraint failed: profiles.url (SQL: insert into "profiles" ("title", "description", "user_id", "updated_at", "created_at") values (Cool, Desc, 1, 2020-03-12 02:03:16, 2020-03-12 02:03:16))' I am attaching a Profile to a User and my User table has contents: >> User::all() => Illuminate\Database

问题 I'm studying Laravel and working around in php artisan but I keep on getting this error: Illuminate/Database/QueryException with message 'SQLSTATE[23000]: Integrity constraint violation: 19 NOT NULL constraint failed: profiles.url (SQL: insert into "profiles" ("title", "description", "user_id", "updated_at", "created_at") values (Cool, Desc, 1, 2020-03-12 02:03:16, 2020-03-12 02:03:16))' I am attaching a Profile to a User and my User table has contents: >> User::all() => Illuminate\Database

问题 I'm studying Laravel and working around in php artisan but I keep on getting this error: Illuminate/Database/QueryException with message 'SQLSTATE[23000]: Integrity constraint violation: 19 NOT NULL constraint failed: profiles.url (SQL: insert into "profiles" ("title", "description", "user_id", "updated_at", "created_at") values (Cool, Desc, 1, 2020-03-12 02:03:16, 2020-03-12 02:03:16))' I am attaching a Profile to a User and my User table has contents: >> User::all() => Illuminate\Database

问题 DataBase movies.db tables directors (movie_id, person_id) movies (id, title, year) people (id, name, birth) ratings (movie_id, rating, votes) stars (movie_id, person_id) you can download the database . Question I'm new in programming, so I decided, to begin with, CS50 Harvard course here is the problem and the test solution: In 13.sql, write a SQL query to list the names of all people who starred in a movie in which Kevin Bacon also starred. Your query should output a table with a single