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Create Database Artifacts Using Core Data Services (CDS) for SAP HANA Cloud

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Create Database Artifacts Using Core Data Services (CDS) for SAP HANA Cloud
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Create Database Artifacts Using Core Data Services (CDS) for SAP HANA Cloud

February 14, 2021
Created by
February 5, 2021
Use SAP Cloud Application Programming Model (CAP) and Core Data Services (CDS) to generate SAP HANA Cloud basic database artifacts.

You will learn

  • How to use SAP Cloud Application Programming Model (CAP) Core Data Services (CDS) to create simple database entities
  • How to define database-agnostic artifacts in the persistence module
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Prerequisites

The SAP 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 Cloud. For this reason, you will also create two tables that do not require any advanced data types.


Step 1: Create database entities
  1. In the db folder, right mouse click and choose New File

    New File
  2. Use the following name:

    interactions.cds
    
    Interactions.cds
  3. Use the following content in this new file:

    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  : Composition of 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 relationships between 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.

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Step 2: Create service interface
  1. In the srv folder created another file and name it interaction_srv.cds

    interaction_srv.cds
    
    interaction_srv.cds
  2. Use the following content in this new file:


    using app.interactions from '../db/interactions'; service CatalogService { entity Interactions_Header as projection on interactions.Interactions_Header; entity Interactions_Items as projection on interactions.Interactions_Items; }
  3. Save all.

    What is going on?

    You are declaring services to expose the database entities you declared in the previous step.

  4. From the terminal issue the command: cds build

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

    cds build log
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Step 3: Explore generated design-time artifacts
  1. 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.

    Results of cds build
  2. You will now deploy those objects into the HANA Database creating tables and views. We will use the SAP HANA Projects view to do this. Please expand this view and you will see the following:

    SAP HANA Projects view
  3. We need to bind our project to a Database Connection and HDI container instance. Press the bind icon to being the process.

    Bind Project
  4. The bind process will start a wizard where you will be prompted for values via the command pallet at the top of the SAP Business Application Studio screen. You might be asked to confirm your Cloud Foundry endpoint and credentials depending upon how long it has been since you last login.

    Confirm Credentials
  5. You might be presented with options for existing service instances (if you’ve completed other tutorials or have performed other HANA development). But for this exercise we want to choose Create a new service instance

    Create a new service instance
  6. Press enter to accept the generated service name

    Generated Service Name
  7. It will take a minute or two for the service to be created in HANA. A progress bar will be shown in the message dialog

    Service Creation Progress
  8. Upon completion, the Database Connections will now show the service bound to the instance the wizard just created.

    Bound Connection
  9. We are now ready to deploy the development content into the database. Press the Deploy button (which looks like a rocket) at the db folder level in the SAP HANA Projects view.

    Deploy
  10. 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

You can find a similar example and further context on Core Data and Services in this explanatory video

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Step 4: Check the Database Explorer

You can now check the generated tables and views in the Database Explorer.

  1. In the SAP HANA Projects view, press the Open HDI Container button

    Press Open HDI Container
  2. The Database Explorer will open in a new browser tab and automatically select the database entry for your project’s HDI container.

  3. Once open, navigate to the Tables section and click on the Header table.

    Open Table Definition
  4. Note the name of the table matches the generated hdbtable artifacts. You will also see the physical schema managed by the HDI container.

    Unless a name is specified during deployment, HDI containers are automatically created with names relative to the project and user generating them. This allows developers to work on different versions of the same HDI container at the same time.
    Build database module

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Step 5: Load data into your tables
  1. Download the header file and the items file into your local file system.

  2. Right-click again on the header table and choose Import Data.

    Import data
  3. Choose Import Data and press Step 2

    Import data
  4. Choose Local for the Import Data From: option. Browse for the Header file and click Step 3.

    Import data
  5. Keep the default import target and click Step 4.

    Import data
  6. Keep the default table mapping and press Step 5.

    Import data
  7. Keep the default error handling and press Review

    Import data
  8. Choose Import into Database.

    Import data
  9. You will see confirmation that 4 records have imported successfully.

    Import data
  10. Repeat the process with the Items.csv file into the Items table.

    Import data
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Step 6: Check data loaded into the tables
  1. You can now check the data loaded into the tables. Right-click on the Items table and click Generate Select Statement.

    Generate select statement
  2. Add the following WHERE clause to the SELECT statement and execute it to complete the validation below.

    where "LOGTEXT"  like '%happy%';
    
Which results appear under `TEXT_ID`?
×

Next Steps

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