Added Fetching from Database documentation (#3600)

Author: PascalSenn

website/src/docs/hotchocolate/fetching-data/fetching-from-databases.md

@@ -2,12 +2,168 @@
 title: "Fetching from Databases"
 ---
 
-Hi,
+import { ExampleTabs } from "../../../components/mdx/example-tabs"
 
-We're currently working on the version 11 documentation. Probably right now at this very moment. However, this is an open-source project, and we need any help we can get! You can jump in at any time and help us improve the documentation for hundreds or even thousands of developers!
+In this section, you find a simple example on how you can fetch data from a database and expose it as a GraphQL API.
 
-In case you might need help, check out our slack channel and get immediate help from the core contributors or the community itself.
+**HotChocolate is not bound to a specific database, pattern or architecture.**
+[We do have a few integrations](/docs/hotchocolate/integrations), that help with a variety of databases, though these are just additions on top of HotChocolate.
+You can couple your business logic close to the GraphQL server, or cleanly decouple your domain layer from the GraphQL layer over abstractions.
+The GraphQL server only knows its schema, types and resolvers, what you do in these resolvers and what types you expose, is up to you. 
+
+In this example, we will directly fetch data from MongoDB in a resolver. 
+
+# Setting up the Query
+The query type in a GraphQL schema is the root type. Each field defined on this type is available at the root of a query. 
+If a field is requested, the resolver of the field is called. 
+The data of this resolver is used for further execution.
+If you return a scalar, value (e.g. `string`, `int` ...) the value is serialized and added to the response.
+If you return an object, this object is the parent of the resolver in the subtree.
+
+<ExampleTabs>
+<ExampleTabs.Annotation>
+
+```csharp
+// Query.cs
+public class Query
+{
+    public Task<Book?> GetBookById(
+        [Service] IMongoCollection<Book> collection,
+        Guid id)
+    {
+        return collection.Find(x => x.Id == id).FirstOrDefaultAsync();
+    }
+}
+
+// Book.cs
+public class Book
+{
+    public string Title { get; set; }
+
+    public string Author { get; set; }
+}
+
+// Startup.cs
+public class Startup
+{
+    public void ConfigureServices(IServiceCollection services)
+    {
+        services
+            .AddRouting()
+            .AddGraphQLServer()
+            .AddQueryType<Query>();
+    }
+
+    // Omitted code for brevity
+}
+```
+
+</ExampleTabs.Annotation>
+<ExampleTabs.Code>
+
+```csharp
+// Query.cs
+public class Query
+{
+    public Task<Book?> GetBookById(
+        [Service] IMongoCollection<Book> collection,
+        Guid id)
+    {
+        return collection.Find(x => x.Id == id).FirstOrDefaultAsync();
+    }
+}
+
+// QueryType.cs
+public class QueryType : ObjectType<Query>
+{
+    protected override void Configure(IObjectTypeDescriptor<Query> descriptor)
+    {
+        descriptor
+            .Field(f => f.GetBookById(default!, default!))
+            .Type<BookType>();
+    }
+}
+
+// Book.cs
+public class Book
+{
+    public string Title { get; set; }
+
+    public string Author { get; set; }
+}
+
+// BookType.cs
+public class BookType : ObjectType<Book>
+{
+    protected override void Configure(IObjectTypeDescriptor<Query> descriptor)
+    {
+        descriptor
+            .Field(f => f.Title)
+            .Type<StringType>();
+
+        descriptor
+            .Field(f => f.Author)
+            .Type<StringType>();
+    }
+}
+
+
+// Startup.cs
+public class Startup
+{
+    public void ConfigureServices(IServiceCollection services)
+    {
+        services
+            .AddRouting()
+            .AddGraphQLServer()
+            .AddQueryType<QueryType>();
+    }
+
+    // Omitted code for brevity
+}
+```
+
+</ExampleTabs.Code>
+<ExampleTabs.Schema>
+
+```csharp
+// Query.cs
+public class Query
+{
+    public Task<Book?> GetBookById(
+        [Service] IMongoCollection<Book> collection,
+        Guid id)
+    {
+        return collection.Find(x => x.Id == id).FirstOrDefaultAsync();
+    }
+}
+
+// Startup.cs
+public class Startup
+{
+    public void ConfigureServices(IServiceCollection services)
+    {
+        services
+            .AddRouting()
+            .AddGraphQLServer()
+            .AddDocumentFromString(@"
+                type Query {
+                  bookById(id: Uuid): Book
+                }
+
+                type Book {
+                  title: String
+                  author: String
+                }
+            ")
+            .BindComplexType<Query>();
+    }
+
+    // Omitted code for brevity
+}
+```
+
+</ExampleTabs.Schema>
+</ExampleTabs>
 
-Sorry for any inconvenience, and thank you for being patient!
 
-The ChilliCream Team