Defining a Basic CDS View

To create a new data definition, proceed as follows:

1. Right-click on your project in the Project Explorer.
2. Choose New → ABAP Repository Object …
3. From the list, choose Core Data Services → Data Definitions.
   Hint

   You can use the input field below Project to type a search term, for example data def.

4. Choose Next.
5. Enter the name of an existing package, and a name and description for the new data definition.
   Hint

   If you enter the name of a database table or the name of a CDS View entity as Referenced Object, the new view will read all fields from that referenced object.

If your package already contains a data definition, you can use the following shortcut:

1. In the Project Explorer, expand the subnode Core Data Services → Data Definitions of the favorite package.
2. Right-click Data Definitions and choose New Data Definition.

When you create a new data definition, you can begin with a blank page. Alternatively, you can use one of several available templates as a starting point. The recommended template when defining a simple view is Define View Entity.

Usually, a respective dialog appears after you assign the new data definition to your transport request. But you can always return to the template selection later in the editing process.

To choose a template later, go to the Templates tab in the tabstrip below the editor window.

A CDS view never stores data by itself. It always references one or more data sources from which it reads the data.

The data foundation of a CDS view is specified in the define statement after keyword FROM. Here you can specify database tables and other CDS views.

Play the video to learn about the element list.

The keyword KEY makes a view element part of the views key. The key elements have to be placed in one block at the beginning of the element list.

For a CDS view, it is not mandatory to define a key but it is strongly recommended. You will see a warning from the syntax check if the view does not contain at least one key element.

There is another warning if the key of the CDS view does not match the key of its data source. There can be reasons to ignore this warning but usually the key of the view should be identical to the key of the data source. There is one general exception though: If the data source is a database table with a client field, this client field should not be part of the element list of the view.

With the AS addition, you can define a name for an element. If an element is just a field of the data source, the AS addition is optional. In that case, the name stays the same as in the data source.

Instead of adding the fields of the data source one by one, you can press Ctrl + Space and choose Insert all elements. This template not only adds all fields of the data source (except for the client field) to the element list, it also takes over the key definition and suggests alias names in mixed-case for all fields.

The syntax that we use in data definitions is called the CDS Data Definition Language (DDL). To increase readability you can let ADT format the DDL source. Place the cursor somewhere in the data definition and choose Source Code → Format from the Eclipse menu or press Ctrl + F1.

By default, Eclipse uses a standard formatter profile that it derives from the ABAP system. You can define your own formatter profiles in the Eclipse Preferences dialog. Choose Window → Preferences from the eclipse menu and search for DDL Formatter.

Play the video to learn about comments in CDS DDL.