SetON CASCADE DELETEon relation in database. This will instruct SQL to delete all related records whichwere not loaded to contextin the time of deleting the parent. The implementation of cascade deletes in EF is strange and quite inefficient but this is how it behaves and if you want to us...
EF是Entity Framework的缩写,是微软推出的一种ORM(对象关系映射)框架,用于简化开发人员与数据库之间的交互。它提供了一种将数据库表映射到.NET对象的方式,使开发人员可以使用面向对象的方式进行数据库操作。 在EF中,如果我们删除一个父记录,而不删除子记录,可能有以下几个原因: 数据完整性:子记录可能与其他父记录存...
Tip The code shown here comes from ExecuteDeleteSample.cs.Calling ExecuteDelete or ExecuteDeleteAsync on a DbSet immediately deletes all entities of that DbSet from the database. For example, to delete all Tag entities:C# Copy await context.Tags.ExecuteDeleteAsync(); ...
("All blogs in database:"); var temp = string.Empty; foreach (var blog in db.Blogs) { Console.WriteLine(" - {0}", blog.Url); temp += DateTime.Now + JsonConvert.SerializeObject(blog) + "\r"; } StringValue = temp; } } public async Task DMDeleteAsync() { using (var db = ...
{ // 多次插入单条记录 int count = connection.Execute...into Posts values(@CategoryId, @Slug, @Title, @Published, @Excerpt, @Content);", postRecords); ④ 如何跨数据库读取数据记录...单张表 2.7s 读取MSSQL连接查询 2.6s 读取MSSQL多个结果集 2.8s 多次插入MSSQL新记录 148ms 三、Peta...
Add, modify, and delete data by calling methods on the entities. Map multiple database tables to a single C# entity. Handle concurrency issues that arise when multiple users simultaneously attempt to update the same record. Use the LINQ (System.Linq) syntax to query the database. Access multi...
This aligns with complex types having no key for identity and hence a complex type instance is equal to another complex type instance if and only if all their members are equal. Notice that this also aligns with equality for C# records. Manipulation of complex type values EF8 provides access...
Using this library, Entity Framework Core users can delete or update multiple records from a LINQ Query in a SQL statement without loading entities. This libary supports Entity Framework Core 5.0 and Entity Framework Core 6.0. Instructions: Step 1 As for.NET 5 users: SQLServer: Install-Package ...
Once a new migration has been generated, it can be applied to a database in various ways. EF Core records all applied migrations in a special history table, allowing it to know which migrations have been applied and which haven’t.
records批量插入 mysql利用LOAD语句实现数据批量录入 本章的前面讨论如何使用SQL向一个表中插入数据。但是,如果你需要向一个表中添加许多条记录,使用SQL语句输入数据是很不方便的。幸运的是,MySQL提供了一些方法用于批量录入数据,使得向表中添加数据变得容易了。本节以及下一节,将介绍这些方法。本节将介绍SQL语言级的...