sqlite | 易学教程

How to save nested List<String> in RoomDB on Android

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问题 Hey google have an example on using @Relation @Entity public class Pet { int userId; String name; // other fields } public class UserNameAndAllPets { public int id; public String name; @Relation(parentColumn = "id", entityColumn = "userId") public List<Pet> pets; } Is it possible to save list of String without creating extra class for it. I want to avoid incosistence between my JsonProperty and a room Entity W would like to have soemthing like that public class UserNameAndAllPets {

Django makemigrations works, migrate fails with “django.db.utils.IntegrityError: NOT NULL constraint failed”

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问题 I'm stuck. Django 1.7, SQLite3. I've changed my model to add the thumbnail column, as in this tutorial. It was this: from django.db import models class Article(models.Model): title = models.CharField(max_length=200) body = models.TextField() pub_date = models.DateTimeField('date published') likes = models.IntegerField(default=0) def __str__(self): return self.title and is now this: from django.db import models from time import time def get_upload_file_name(instance, filename): return

How to save image data to sqflite database in flutter for persistence

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问题 I'm building a Flutter app where I would like to keep the data offline. I'm capturing an image using the camera or gallery image picker and able to store that image into a File image variable. File _avatarImg; void _getImage(BuildContext context, ImageSource source) { ImagePicker.pickImage( source: source, maxWidth: 400.0, maxHeight: 400.0, ).then((File image) { _avatarImg = image; }); } This works perfectly however my question is, how would I go about storing this image for persistence?

How to save image data to sqflite database in flutter for persistence

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How to calculate square root in sqlite

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问题 I need to calculate an euclidean distance in a sqlite database. Does anyone know how to calculate square roots in sqlite beside writing and loading a dynamic library for math functions? I am close to resorting to the fast inverse square root algorithm in here http://en.wikipedia.org/wiki/Fast_inverse_square_root though it might to turn into more fun than I need right now. And as a side note, it'd be great to figure out how to do power (which is the generalized question, and is cleaner coding

Xamarin Forms, Sqlite, EF Core 3, migrations, and lot of confussion

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问题 I have a Xamarin Forms app that I have switched from using only restful API to using local SQLite DB, that will sync using this Dotmim.Sync - DB Sync'ing Framework (which is great!). I am using EF Core 3 in the Xamarin forms project to interact with SQLite. My questions are around running migrations or just database updates on SQLite. I have read several blogs and forums about different approaches, but they all are several years old, from EF Core 1 to EF Core 2, and lots of work around. https

Django+Nginx+uwsgi搭建自己的博客（一）

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最近对写爬虫有些厌倦了，于是将方向转移到了Web开发上。其实在之前自己也看过一部分Flask的资料，但总觉得Flask的资料有些零散，而且需要的各种扩展也非常多。因此，我将研究方向转移到了另一个主流的框架——Django上。与Flask框架相比，Django框架提供了更全面的文档支持，其初始教程也很容易上手。而且，相比Flask，Django并不需要很多扩展的支持，其自身就提供了很多便利的类。个人感觉这两点使得学习Django比学习Flask更容易上手。目前，Python3已经成为了主流版本，因此此文采用Python3.5进行开发。环境：Ubuntu16.04+Python3.5 首先看一下目前的成果：首页列出了当前所有博客的列表，包括作者，阅读量以及发表时间；在页面左上角是用户名以及该用户的头像，而右边可以退出登录以及发表博文。点击博文，可以浏览到博文内容，以及发表评论并查看评论。点击已注册的用户名，可以查看到该用户的相关资料。下面来介绍Django的几个基本概念：Project, App, Model, View Project和App: 一个Django project即是一个网站，而App可以看为网站中的子功能。一个project里可以包含多个App，通过这些App的共同作用来实现网站的功能。 Model: 即数据库表模型

[NewLife.XCode]功能设置

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NewLife.XCode是一个有10多年历史的开源数据中间件，由新生命团队(2002~2019)开发完成并维护至今，以下简称XCode。整个系列教程会大量结合示例代码和运行日志来进行深入分析，蕴含多年开发经验于其中，代表作有百亿级大数据实时计算项目。开源地址： https://github.com/NewLifeX/X （求star, 652+）连接字符串 XCode支持SqlServer、SQLite、MySql、Oracle、PostgreSQL、Access、SqlCe等多种数据库，常用连接字符串模板如下： < add name ="SQLite" connectionString ="Data Source=test.db;" providerName ="Sqlite" /> < add name ="MySql" connectionString ="Server=.;Port=3306;Database=mysql;Uid=root;Pwd=;" providerName ="MySql.Data.MySqlClient" /> < add name ="MSSQL" connectionString ="Server=.;User ID=sa;Password=sa;Database=Test;datapath=~\App_Data"

How to write a Pandas Dataframe to existing Django model

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问题 I am trying to insert data in a Pandas DataFrame into an existing Django model, Agency , that uses a SQLite backend. However, following the answers on How to write a Pandas Dataframe to Django model and Saving a Pandas DataFrame to a Django Model leads to the whole SQLite table being replaced and breaking the Django code. Specifically, it is the Django auto-generated id primary key column that is replaced by index that causes the errors when rendering templates ( no such column: agency.id ).

C# SQLite Insert Datetime type Value

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问题 I want Insert DateTime Type Value.But I got this Error Source Code private void Execute(string query) { SQLiteCommand cmd = new SQLiteCommand(query, conn); int result = cmd.ExecuteNonQuery(); Debug("Executed query: {0} Result: {1}", query, result); } private string DEscape(DateTime time) { return time.ToString(@"\'yyyy-MM-dd\'"); } public void InsertVideo(string videoID, DateTime releaseDate, string[] genres) { string genreStr = ""; foreach (string g in genres) { genreStr = genreStr +