Core Data Services (CDS) views are an integral part of SAP HANA development, and they are widely used to define semantically rich database views on top of other SAP HANA database objects, such as tables and other CDS views. As a result, CDS views are a popular topic of discussion in SAP HANA interviews.
If you are preparing for an SAP HANA interview, it is important to be familiar with the most common CDS views interview questions. These questions can range from the basics, such as “What is a CDS view?” to more advanced topics, such as “How do you use Association and Path expressions in ABAP HANA CDS?”
To help you prepare for your SAP HANA interview, we have compiled a list of the top CDS views interview questions and answers. By reviewing these questions and answers, you can gain a better understanding of the most important CDS views concepts and be better prepared to answer questions related to them during your interview.
Understanding CDS Views
CDS views are an important entity in SAP ABAP HANA, which allows developers to define semantically rich database views on top of other SAP HANA database objects such as tables and other CDS views. CDS views provide an extra layer of abstraction to the database objects, which makes it easier to understand and use the data.
Core Data Services (CDS) is a service provided by HANA core, which allows developers to create re-usable SQL logic. CDS views can be enriched with metadata, which makes them even more useful than just a pile of dumb data. CDS views are database artifacts that can be created, modified, and accessed using ADT with Eclipse.
There are many types of ABAP HANA CDS views, including basic CDS views, composite CDS views, and consumption CDS views. Basic CDS views are the simplest type of CDS view, which are used to project fields from one or multiple tables. Composite CDS views are used to combine the data from multiple basic CDS views or tables. Consumption CDS views are used to consume the data from other CDS views or tables.
CDS entities are the building blocks of CDS views. CDS entities can be tables, views, or other CDS entities. CDS entities can be defined in a CDS file, which is a text file with a .cds extension. CDS entities can be used to define the structure of a CDS view, which makes it easier to understand and use the data.
In summary, CDS views are an essential entity in SAP ABAP HANA, which allows developers to define semantically rich database views on top of other SAP HANA database objects. CDS views provide an extra layer of abstraction to the database objects, which makes it easier to understand and use the data. CDS entities are the building blocks of CDS views, which can be tables, views, or other CDS entities.
Role of ABAP in CDS Views
ABAP (Advanced Business Application Programming) is a high-level programming language used to develop enterprise-level applications for the SAP platform. ABAP is an integral part of CDS (Core Data Services) views, which are semantically rich database views used in SAP HANA. In this section, we will explore the role of ABAP in CDS views.
ABAP is used in CDS views to define the data model and implement the business logic. It is used to create and maintain the data dictionary objects, such as tables, views, and data types, which are used in CDS views. ABAP code logic is used to define the relationships between the data dictionary objects and to implement the business rules.
ABAP Core Data Services (CDS) is a framework that allows developers to define semantically rich data models in ABAP. CDS views are used to define the data model and business logic in a single view. ABAP CDS views provide an extra layer of abstraction to the database objects, which makes it easier to develop and maintain complex applications.
ABAP CDS views use code push down technique and data virtualization for data fetching from the much faster HANA database. This means that the data processing is performed in the database layer, which reduces the load on the application server and improves performance. ABAP CDS views also support the latest innovations in CDS after ABAP 7.50, which help to reduce ABAP code logic and conditions on the application layer.
In summary, ABAP plays a crucial role in CDS views by defining the data model and implementing the business logic. ABAP Core Data Services (CDS) is a powerful framework that allows developers to define semantically rich data models in ABAP and provides an extra layer of abstraction to the database objects. ABAP CDS views use code push down technique and data virtualization for data fetching from the HANA database, which improves performance and reduces the load on the application server.
CDS Views and SQL
CDS views are an essential part of SAP HANA and ABAP development. They provide an extra layer of abstraction to the database objects and allow developers to define semantically rich database views on top of other SAP HANA database objects, such as tables and other CDS views.
CDS views use SQL syntax to define the underlying ABAP Data Dictionary (DDIC) structure. The SQL syntax used in CDS views is similar to the SQL syntax used in Open SQL, but with some additional features. For example, CDS views support various annotations that can be used to provide additional information about the view or its elements.
One of the most powerful features of CDS views is their ability to define SQL views. SQL views are virtual tables that are based on one or more tables or other views. They can be used to simplify complex queries, hide sensitive data, or provide a consistent interface to data from different tables.
To define a SQL view in a CDS view, you can use the @AbapCatalog.sqlViewName annotation. This annotation specifies the name of the SQL view that will be generated based on the CDS view definition. You can also use the @AbapCatalog.compiler.compareFilter annotation to specify a filter that will be applied to the SQL view.
CDS views also support the SELECT statement, which is used to retrieve data from one or more tables or views. The SELECT statement can be used to specify the columns to be retrieved, filter the rows to be returned, and sort the results. You can use the SELECT statement in a CDS view to define the projection of the view, which specifies the columns that will be included in the view.
In addition to the SELECT statement, CDS views also support various other SQL statements, such as JOIN, UNION, and GROUP BY. These statements can be used to combine data from multiple tables or views, perform aggregations, and more.
Overall, CDS views provide a powerful and flexible way to work with data in SAP HANA and ABAP. By using SQL syntax and supporting SQL views, CDS views make it easy to define semantically rich views on top of other database objects.
CDS Views in SAP HANA
CDS (Core Data Services) views are an essential feature of SAP HANA. They provide a semantically rich layer of abstraction on top of the database objects, such as tables and other CDS views. CDS views are used to define reusable SQL logic, which can be simple projections of table fields or more complex calculations, aggregations, joins, and unions.
CDS views are defined using the CDS language, which is an extension of SQL. The CDS language provides a set of annotations that can be used to define the structure and behavior of the CDS view. These annotations can be used to define the data model, the SQL view name, the authorization check, and more.
The HANA database provides several types of CDS views, including basic views, composite views, and consumption views. Basic views are used to define a simple projection of table fields, while composite views are used to define a more complex data model that includes joins, unions, and aggregations. Consumption views are used to define a view that can be consumed by other applications, such as SAP Fiori.
SAP HANA CDS views are widely used in SAP applications, and it is essential for SAP developers to have a good understanding of CDS views. During interviews, candidates may be asked questions related to the different types of CDS views, the CDS annotations, the underlying ABAP Data Dictionary structure, and more. It is essential to have a good understanding of these topics to perform well in an interview.
In conclusion, CDS views are a critical feature of SAP HANA. They provide a semantically rich layer of abstraction on top of the database objects, and they are widely used in SAP applications. It is essential for SAP developers to have a good understanding of CDS views to perform well in an interview.
Annotations and Metadata in CDS Views
Annotations and metadata in CDS views are important elements that help developers to define semantically rich database views on top of other SAP HANA database objects, such as tables and other CDS views. Annotations are a way to add ABAP and component-specific metadata to the source code of any CDS entity. They can control technical settings, buffering, and several other properties that annotations can control.
One of the most commonly used annotations in CDS views is @AbapCatalog.sqlViewName. This annotation is used to define the name of the SQL view that is created in the ABAP Dictionary when the CDS view is activated. Another useful annotation is @EndUserText.label. This annotation is used to define the label that is displayed to the end-user in the user interface.
Metadata, on the other hand, is information that describes the data itself. In CDS views, metadata is used to enrich the view with additional information that makes it more useful than just a pile of dumb data. For example, metadata can be used to define the data type, length, and other characteristics of a field in the view.
When defining a CDS view, it is important to include annotations and metadata to provide additional context and information about the view. This can help other developers to understand what the view is used for and how it should be used.
In summary, annotations and metadata are important elements in CDS views that help to define semantically rich database views on top of other SAP HANA database objects. Annotations can control technical settings, buffering, and several other properties, while metadata is used to enrich the view with additional information about the data itself. It is important to include annotations and metadata when defining a CDS view to provide additional context and information about the view.
OData Services and CDS Views
OData services are a powerful way to expose data to external systems and applications in a standardized way. SAP Gateway is the recommended way to expose OData services from an SAP system. OData services can be based on CDS views, which provide a way to define complex data models in a declarative way.
To publish a CDS view as an OData service, we need to define an OData service and map it to the CDS view. This can be done using the SAP Gateway Service Builder transaction (/IWFND/MAINT_SERVICE). The service builder allows us to define the OData service metadata, which describes the structure of the service and the entities it exposes.
Once the service metadata is defined, we can map the CDS view to an OData entity set. This allows us to expose the data in the CDS view as a collection of entities in the OData service. We can also define navigation properties between entities, which allows us to navigate between related data in the service.
When publishing a CDS view as an OData service, it’s important to consider the performance implications. CDS views can be optimized for performance using techniques such as aggregation, filtering, and projection. These optimizations can be leveraged when exposing the CDS view as an OData service, but it’s important to test the performance of the service to ensure that it meets the requirements of the consuming systems and applications.
Overall, OData services and CDS views provide a powerful way to expose data from SAP systems in a standardized way. By leveraging the capabilities of SAP Gateway and CDS views, we can create efficient and flexible services that can be consumed by a wide range of external systems and applications.
Table Functions and Associations
Table functions are an essential part of CDS views. They allow developers to perform complex logic and significantly simplify the overall VDM architecture. Table functions are defined using the ABAP CDS statement DEFINE TABLE FUNCTION and can be used as the data source in Open SQL read statements. Each CDS table function includes the following components:
- The actual CDS entity of the table function that is generated in the ABAP Dictionary.
- The CDS table function implementation (ABAP class library).
Associations in CDS views enable developers to define relationships between tables. They are similar to joins in SQL, but they are more powerful and flexible. Associations are defined with Cardinality, which specifies the number of records that can be returned by the association.
Path expressions are used to navigate through the associations in CDS views. They are used to extract data from the associated tables and can be used to filter, group, and order data. Path expressions are defined using the -> operator, which is similar to the . operator used in ABAP.
Associations and path expressions can significantly simplify the development of CDS views. They allow developers to define complex relationships between tables and extract data from multiple tables in a single query. However, they can also be challenging to use correctly, and developers must have a good understanding of their behavior to avoid performance issues.
In summary, CDS table functions, associations, and path expressions are powerful tools that can significantly simplify the development of CDS views. They enable developers to define complex relationships between tables and extract data from multiple tables in a single query. However, they can also be challenging to use correctly, and developers must have a good understanding of their behavior to avoid performance issues.
Best Practices for CDS Views
CDS views are a powerful tool for creating semantically rich database views in SAP HANA. To ensure that your CDS views are optimized for performance and maintainability, it is important to follow some best practices. In this section, we will discuss some of the best practices for CDS views.
Use Latest Innovations in CDS After ABAP 7.50
It is recommended to use the latest innovations in CDS after ABAP 7.50. These innovations can help reduce ABAP code logic and conditions on the application layer. CDS executes at the database layer, making the application faster. Additionally, CDS can publish oData services on the fly, which can be consumed directly by Fiori reports effortlessly.
Code Push Down Technique
CDS views should be designed using the code push down technique. This technique involves pushing as much logic as possible to the database layer. By doing so, the application layer can be kept lightweight, and the database layer can handle the heavy lifting. This approach can improve performance and scalability.
Data Virtualization
CDS views can be used to create virtual data models. This approach is known as data virtualization. By creating virtual data models, you can avoid duplicating data and reduce storage costs. Additionally, virtual data models can be easily updated, and changes can be propagated to all applications that use them.
Data Model Design
When designing data models for CDS views, it is important to follow best practices for data modeling. This includes using standard naming conventions, avoiding redundant data, and creating clear relationships between entities. Additionally, data models should be designed with scalability in mind, so they can easily accommodate future changes and growth.
In conclusion, following best practices for CDS views can help ensure that your database views are optimized for performance and maintainability. By using the latest innovations in CDS, code push down techniques, data virtualization, and good data model design, you can create powerful and flexible data models that can be easily consumed by applications.
AMDP and CDS Views
ABAP Managed Database Procedures (AMDP) and Core Data Services (CDS) views are two important concepts in SAP ABAP HANA. Both AMDP and CDS views are used to fetch data from the database, but they differ in their approach and functionality.
AMDP is a database procedure that is defined in ABAP and executed in the database. It is a global class with the implemented interface IF_AMDP_MARKER_HDB. AMDP can be used to perform complex calculations and data transformations that are not possible with CDS views. AMDP can also be used to call external procedures or functions.
On the other hand, CDS views are database entities that are used to fetch data from DDIC/Standard CDS views or any other data sources. CDS views can be enriched with metadata, making them more useful than just a pile of dumb data. CDS views can also be used to join multiple tables and perform basic calculations.
Here are some differences between AMDP and CDS views:
| AMDP | CDS Views |
|---|---|
| Defined in ABAP and executed in the database | Defined in the database |
| Can perform complex calculations and data transformations | Can perform basic calculations |
| Can call external procedures or functions | Cannot call external procedures or functions |
| Not suitable for simple queries | Suitable for simple queries |
| Can be used for data analysis and reporting | Can be used for data analysis and reporting |
In conclusion, both AMDP and CDS views are important concepts in SAP ABAP HANA. AMDP is suitable for complex calculations and data transformations, while CDS views are suitable for simple queries and data analysis. Understanding the differences between AMDP and CDS views can help you choose the right tool for the job.
Security Aspects in CDS Views
When it comes to CDS views, security is an important aspect that needs to be considered. As CDS views are used to access data from various tables, it’s important to ensure that the data is accessed only by authorized users. Here are some security aspects to consider when working with CDS views:
Define Role
A Define Role is a collection of authorizations that are required to perform a specific task. When creating CDS views, it’s important to ensure that the Define Role is properly defined. This will ensure that only authorized users are able to access the data.
PFCG
PFCG (Profile Generator) is a tool that is used to create and maintain authorization profiles. When working with CDS views, it’s important to ensure that the PFCG is properly configured. This will ensure that only authorized users are able to access the data.
PFCG Based Role Access
PFCG Based Role Access is a security mechanism that is used to restrict access to specific data. When working with CDS views, it’s important to ensure that the PFCG Based Role Access is properly configured. This will ensure that only authorized users are able to access the data.
In summary, security is an important aspect to consider when working with CDS views. It’s important to ensure that the Define Role, PFCG, and PFCG Based Role Access are properly configured to ensure that only authorized users are able to access the data.
Debugging CDS Views
Debugging CDS Views can be a challenging task, but with the right approach, it can be done efficiently. Here are some tips to help you debug your CDS Views:
Use the True and False Parameters
One of the easiest ways to debug your CDS Views is by using the true and false parameters. When you set the debug parameter to true, the system will stop at the breakpoint you have set, and you can then step through the code to see where the problem lies. On the other hand, when you set the debug parameter to false, the system will not stop at the breakpoint, and the code will execute as normal.
Check the Syntax
Another common issue when debugging CDS Views is syntax errors. It is essential to check the syntax of your code to ensure that there are no errors. One way to do this is by using the syntax check feature in the ABAP Development Tools (ADT). The syntax check will highlight any syntax errors in your code, making it easier to fix them.
Use the Debugging Tools
When debugging CDS Views, it is also essential to make use of the debugging tools available in ADT. The debugging tools allow you to step through the code, set breakpoints, and view variables and their values. Some of the debugging tools available in ADT include the Debug Perspective, the Debugger, and the Variables View.
Test with Sample Data
Finally, it is a good idea to test your CDS Views with sample data. This will help you identify any issues with your code before it goes into production. You can use the Data Preview feature in ADT to test your CDS Views with sample data.
In conclusion, debugging CDS Views can be a challenging task, but with the right approach, it can be done efficiently. By using the true and false parameters, checking the syntax, using the debugging tools, and testing with sample data, you can identify and fix any issues with your CDS Views.
Interview Questions for CDS Views
If you are a candidate preparing for an interview process related to SAP ABAP HANA CDS views, then you might have some questions about what to expect. Here are some frequently asked questions (FAQ) that might help you prepare:
General Questions
- What is a CDS view in SAP HANA?
- What is the difference between CDS view and database view?
- How do you create a CDS view?
- What are the different types of CDS views in SAP HANA?
- What are the advantages of using CDS views?
Technical Questions
- What is the syntax to define a CDS view?
- What is the difference between @AbapCatalog.sqlViewName and @AbapCatalog.compiler.compareFilter?
- What is the use of @ObjectModel.readOnly annotation?
- What is Association and Path expression in ABAP HANA CDS?
- How do you create a CDS view with parameters?
- What is the difference between a left outer join and a right outer join?
Scenario-Based Questions
- How do you create a CDS view to fetch data from multiple tables?
- How do you create a CDS view to fetch data from a single table with multiple conditions?
- How do you create a CDS view to fetch data from multiple tables with multiple conditions?
- How do you create a CDS view to fetch data from a table with dynamic filters?
- How do you create a CDS view to fetch data from a table with authorization checks?
By preparing for these interview questions, you can demonstrate your knowledge and expertise in SAP ABAP HANA CDS views. Remember to stay confident, knowledgeable, and clear in your answers.