#Android studio sqlite foreign key references how to
You can check the rest of the code to see how to insert, update, and delete. Well, this was a long post but hopefully, useful for you. What do we get when we click on the menu and access the Employees item? First, this query is executed:Īnd the app shows the information from both tables. Then, counting data, inserting values and retrieving the first department (Kitchen). We can see some information in the Output window (in Visual Studio) as well as in the phone: It shouldn't be complicated to understand, but if you do have a question, write a comment and I'll do my best to help :-)
In this post I'm not including the Views definition (because it is pretty obvious, just bindings) or the DetailsView/DetailsViewModel that I use to add, update, or delete information from the tables. The query is used by GetItemsAsync in the ViewModel, while the route is used for navigation.įor the rest of the code, please check the GitHub repository. Thanks to ActivatorUtilities, we can customize this definition by including the following arguments: a query and a route. There you have it! Each View will require a ViewModel, which is the same ( GenericListViewModel) with different generic type and arguments. This is the code of the four classes, in order of creation: I believe that the SQLite attributes are not necessary since we defined our tables using the statements, but it doesn't hurt to include them (I think). I also created a BaseTable class, which includes an Id property, and all classes inherit from this model. For example, the EmployeesAndDepartmentQuery query is a view since it includes fields from Employee (all) and Department (DepartmentName) tables. A view is a projection, a set of specific fields from a query that involves one or several tables. There are two types: models that work as tables, and models that work as views. Create the following classes and structure: I will not include it here, but you can take a look at the GitHub repository for the code. NOTE: In this folder, there is also a FileAccessHelper class which is used to access the database file. However, for Employees table, it is better to customize the data management. For example, you can create and get all items from Departments table with the CreateTable and Table methods because there is no foreign key involved. As you can infer, instead of using the ORM capabilities that are integrated in SQLite, you will manually execute queries! However, you can still use the ORM mapper for several operations. Of course, the most important elements are the statements and queries. two routes (for navigation using Shell)Įnter fullscreen mode Exit fullscreen mode.The second query is a JOIN to demonstrate that the relationship actually exists. two Select queries that return data from the tables.You can observe that Employees include a foreign key restriction. two Create Table statements with the table specification.In Helpers folder, create a Constants class with the following code that includes public constants for: CommunityToolkit.Mvvm (optional, but recommended).
An employee belongs to one department, and the department includes many employees (so there is a 1-N relationship). NET MAUI app that stores information in a local database with 2 tables referenced by a foreign key! In our application, we can perform CRUD operations over two tables: Departments and Employees. Actually, they are supported! Maybe not in the way you'd expect it, but it works. NET MAUI articles posted by community members.Ī common misconception about SQLite-net library is that it can't handle Foreign Keys in a local SQLite database.
NET MAUI Advent Calendar 2022, an initiative led by Héctor Pérez and Luis Beltrán.
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