"How to use core data services to create simple database entities How to define database-agnostic artifacts in the persistence module"

"What do I need before I start?"

" This tutorial is designed for SAP HANA on premise and SAP HANA, express edition. It is not designed for SAP HANA Cloud. You have created an application using the Business Application wizard. "

SAP HANA Native, Create Database Artifacts Using Core Data Services (CDS)

Use core data services to generate SAP HANA basic database artifacts.

🎓beginner ⏱15 min SAP HANA Beginner Express Edition 0/6

Overview

🎓 beginner ⏱ 15 min. SAP HANABeginnerExpress Edition

You will learn

✔How to use core data services to create simple database entities
✔How to define database-agnostic artifacts in the persistence module

T Thomas Jung November 1, 2022

Created by July 25, 2019

Contributors

Prerequisites

This tutorial is designed for SAP HANA on premise and SAP HANA, express edition. It is not designed for SAP HANA Cloud.
You have created an application using the Business Application wizard.

Steps

Open all Close all

Intro

The Cloud Application Programming model utilizes core data services to define artifacts in the database module. Because this model is meant to be database-agnostic – i.e., work with any database – it does not allow you to leverage features that are specific to SAP HANA. For this reason, you will create two tables that do not require any advanced data types.

Step 1 Create database entities

—

In the db module, you will find a file called data-model.cds. Right-click on it and choose Rename.

Use the following name:

Name

interactions.cds

Double-click on the file to open it.

Replace the default contents with the following:

CDS

namespace app.interactions;

using { Country } from '@sap/cds/common';
type BusinessKey : String(10);
type SDate : DateTime;
type LText : String(1024);


entity Interactions_Header {
  key ID : Integer;
  ITEMS  : association to many Interactions_Items on ITEMS.INTHeader = $self;
  PARTNER  : BusinessKey;
  LOG_DATE  : SDate;
  BPCOUNTRY	: Country;

};
entity Interactions_Items {

	key INTHeader : association to Interactions_Header;
	key TEXT_ID : BusinessKey;
		LANGU	: String(2);
		LOGTEXT	: LText;
};

What is going on?
You are declaring two entities with an association to each other. The design-time artifacts declared in this file will be converted to run-time, physical artifacts in the database. In this example, the entities will become tables.

Step 2 Adapt service call

Locate the other cds file (this file may be called cat-service.cds or my-service.cds, depending on the IDE) in the srv folder and rename it.

Use the following name:

Name

interaction_srv.cds

Double-click to open it and replace the existing content with the following:

CDS


using app.interactions from '../db/interactions';
service CatalogService {

 entity Interactions_Header
	@readonly
	as projection on interactions.Interactions_Header;

 entity Interactions_Items
	@readonly
	as projection on  interactions.Interactions_Items;

}

Click Save all.

What is going on?
You are declaring services to expose the database entities you declared in the previous step.

Open the package.json file in the root of your project. Add a section to the cds configuration to include the following

JSON
"hana": {
   "deploy-format": "hdbtable"
}

Right-click on the CDS declaration of the services and choose Build > Build CDS.

Look into the console to see the progress. You can scroll up and see what has been built

Step 3 Explore the generated design-time artifacts

If you pay attention to the build log in the console, you will see the CDS artifacts were converted to hdbtable and hdbview artifacts. You will find those artifacts in a new folder under src called gen.

You will now convert those CDS files specific to SAP HANA into runtime objects (tables). Right-click on the database module and choose Build.

Note: If you get an error during the build process, this could be caused by an older version of the XSA Runtime in HANA, express edition. If your XSA version still contains Node.js version 8.x; this can lead to errors when building because this version of Node.js is no longer supported at the OS level. Newer versions of the XSA runtime only contain Node.js version 10.x and 12.x. If you do receive an error at this point, we would suggest editing the /db/package.json like the following to force the usage of the newer version of the Node.js runtime.

JSON
{
	"name": "deploy",
	"dependencies": {
		"@sap/hdi-deploy": "^3"
	},
	"scripts": {
		"postinstall": "node .build.js",
		"start": "node node_modules/@sap/hdi-deploy/deploy.js"
	},
	"engines": {
		"node": "^10 || ^12"
	}
}

Scroll up to in the console to see what the build process has done.

What is going on?
CDS stands for Core Data Services. This is an infrastructure that allows you to create persistency and services using a declarative language. Notice how you are using the same syntax to define both the persistency and the services. You can find more information on CDS in the help
You defined a CDS artifact, this is an abstraction, a design-time declaration of the entities to be represented in a database and the services to expose them.
Build database module
The original .cds file was translated into hdbtable, which is the SQLDDL syntax specific to SAP HANA when you saved all of the files.
Build database module
These hdbtable files were then translated into runtime objects such as tables in the HANA database.
Build database module
If you checked the services in your space, you would see the service for your HDI container.
Build database module
or for the HANA Cloud trial:
Build database module
You can also check the resources in your space using the resource manager in SAP Web IDE:
Build database module
You can find a similar example and further context on Core Data and Services in this explanatory video