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A CDS view is a data definition that defines a data structure and a data selection from one or more data sources. A CDS view consists of several parts, but two of them are:

Extension: An extension is an optional clause that allows a CDS view to extend another CDS view by adding new elements, annotations, or associations. The extension clause has the syntax EXTEND VIEW view_name WITH view_name. The first view_name is the name of the CDS view that is being extended, and the second view_name is the name of the CDS view that is doing the extension1.

Field list: A field list is a mandatory clause that specifies the elements of the CDS view. The field list has the syntax SELECT FROM data_source { element_list }. The data_source is the name of the data source that the CDS view selects data from, and the element_list is a comma-separated list of elements that the CDS view exposes. The elements can be fields of the data source, expressions, associations, or annotations2.

The following example shows a CDS view that extends another CDS view and defines a field list:

@AbapCatalog.sqlViewName: ‘ZCDS_EXT’ define view Z_CDS_Extension extend view Z_CDS_Base with Z_CDS_Extension as select from ztable { // field list key ztable.id as ID, ztable.name as Name, ztable.age as Age, // extension @Semantics.currencyCode: true ztable.currency as Currency }

The other options are not parts of a CDS view, but rather related concepts:

Partitioning attributes: Partitioning attributes are attributes that are used to partition a table into smaller subsets of data. Partitioning attributes are defined in the ABAP Dictionary for transparent tables and can improve the performance and scalability of data access. Partitioning attributes are not part of the CDS view definition, but rather the underlying table definition3.

Semantic table attributes: Semantic table attributes are attributes that provide additional information about the meaning and usage of a table. Semantic table attributes are defined in the ABAP Dictionary for transparent tables and can be used to enhance the data modeling and consumption of the table. Semantic table attributes are not part of the CDS view definition, but rather the underlying table definition4.

References: 1: Extending CDS Views | SAP Help Portal 2: SELECT List - ABAP Keyword Documentation 3: Partitioning Attributes - ABAP Keyword Documentation 4: Semantic Table Attributes - ABAP Keyword Documentation

Comprehensive and Detailed Step-by-Step Explanation:

Interface Implementation in cl1

The INTERFACES if1 statement in the cl1 definition explicitly declares that cl1 implements the interface if1.

Therefore, option E is correct.

Interface Method Naming in cl1

When an interface is implemented in a class, its methods are accessed using the syntax if1~m1 to distinguish them from other methods in the class.

This makes option C correct.

Usage of if1 in cl2

The DATA mo_if1 TYPE REF TO if1 in cl2 creates a reference variable of type if1. However, it does not mean that cl2 implements or uses the interface if1.

This makes option B incorrect.

Interface Method Naming in cl2

Since cl2 does not implement the interface, it does not inherit its methods. Hence, the method if1~m1 is not available in cl2.

This makes option A incorrect.

Class cl1 and Interface Usage

Class cl1 explicitly states INTERFACES if1, which means it not only implements the interface but also uses it.

This makes option D correct.

References:

SAP ABAP Documentation: Interfaces

SAP Training for Back-End Developer - ABAP Cloud

Based on the given information, the spfli database table should have the following general settings:

“Storage Type” to “Row Store”: This setting determines how the data is stored in the SAP HANA database. Row store is suitable for tables that are accessed by primary key or by a small number of columns. Column store is suitable for tables that are accessed by a large number of columns or by complex analytical queries. Since the spfli table is a large table with over one million rows, and this program is the only one in the system that accesses the table, it is likely that the program will use primary key access or simple queries to access the table. Therefore, row store is a better choice than column store for this table12.

“Load Unit” to “Page Loadable”: This setting determines how the data is loaded into the memory when the table is accessed. Page loadable means that the data is loaded in pages of 16 KB each, and only the pages that are needed are loaded. Column loadable means that the data is loaded in columns, and only the columns that are needed are loaded. Since the spfli table is a row store table, and this program will run rarely, it is more efficient to use page loadable than column loadable for this table. Page loadable will reduce the memory consumption and the loading time of the table13.

References: 1: Table Types in SAP HANA | SAP Help Portal 2: [Row Store vs Column Store in SAP HANA | SAP Blogs] 3: [Load Unit | SAP Help Portal]

The ABAP SQL clause that allows the use of inline declarations is the INTO clause. The INTO clause is used to specify the target variable or field symbol where the result of the SQL query is stored. The INTO clause can use inline declarations to declare the target variable or field symbol at the same position where it is used, without using a separate DATA or FIELD-SYMBOLS statement. The inline declaration is performed using the DATA or @DATA operators in the declaration expression12. For example:

The following code snippet uses the INTO clause with an inline declaration to declare a local variable itab and store the result of the SELECT query into it:

SELECT * FROM scarr INTO TABLE @DATA (itab).

The following code snippet uses the INTO clause with an inline declaration to declare a field symbol and store the result of the SELECT query into it:

SELECT SINGLE * FROM scarr INTO @.

You cannot do any of the following:

FROM: The FROM clause is used to specify the data source of the SQL query, such as a table, a view, or a join expression. The FROM clause does not allow the use of inline declarations12.

INTO CORRESPONDING FIELDS OF: The INTO CORRESPONDING FIELDS OF clause is used to specify the target structure or table where the result of the SQL query is stored. The INTO CORRESPONDING FIELDS OF clause does not allow the use of inline declarations. The target structure or table must be declared beforehand using a DATA or FIELD-SYMBOLS statement12.

FIELDS: The FIELDS clause is used to specify the columns or expressions that are selected from the data source of the SQL query. The FIELDS clause does not allow the use of inline declarations. The FIELDS clause must be followed by an INTO clause that specifies the target variable or field symbol where the result is stored12.

References: 1: SELECT - ABAP Keyword Documentation - SAP Online Help 2: Inline Declarations - ABAP Keyword Documentation - SAP Online Help

The response will be an activation error because the field names of the union do not match. This is because the field names of the union must match in order for the definition to be activated. The union operator combines the result sets of two or more queries into a single result set. The queries that are joined by the union operator must have the same number and type of fields, and the fields must have the same names1. In the given code, the field names of the union do not match, because the first query has the fields carrname, connid, cityfrom, and cityto, while the second query has the fields carrname, carrier_id, cityfrom, and cityto. The field connid in the first query does not match the field carrier_id in the second query. Therefore, the definition cannot be activated.

References: 1: UNION - ABAP Keyword Documentation

A field symbol is a pointer that allows direct access to a row of an internal table without copying it to a work area. Using a field symbol for internal table row access has some advantages over using a work area, such as12:

A MODIFY statement to write changed contents back to the table is not required: This is true. When you use a work area, you have to copy the row content from the internal table to the work area, modify it, and then copy it back to the internal table using the MODIFY statement. This can be costly in terms of performance and memory consumption. When you use a field symbol, you can modify the row content directly in the internal table without any copying. Therefore, you do not need the MODIFY statement12.

Using a field symbol is faster than using a work area: This is true. As explained above, using a field symbol avoids the overhead of copying data between the internal table and the work area. This can improve the performance of the loop considerably, especially for large internal tables. According to some benchmarks, using a field symbol can save 25–40% of the runtime compared to using a work area12.

You cannot do any of the following:

The field symbol can be reused for other programs: This is false. A field symbol is a local variable that is only visible within the scope of its declaration. It cannot be reused for other programs unless it is declared globally or passed as a parameter. Moreover, a field symbol must have the same type as the line type of the internal table that it accesses. Therefore, it cannot be used for any internal table with a different line type12.

The row content is copied to the field symbol instead to a work area: This is false. As explained above, using a field symbol does not copy the row content to the field symbol. Instead, the field symbol points to the memory address of the row in the internal table and allows direct access to it. Therefore, there is no copying involved when using a field symbol12.

References: 1: Using Field Symbols to Process Internal Tables - SAP Learning 2: Access to Internal Tables - ABAP Keyword Documentation - SAP Online Help

In ABAP SQL, an alias is a temporary name that can be assigned to a field or a database table in a query. An alias can be used to make the query more readable, to avoid name conflicts, or to access fields or tables with long names. An alias is created with the AS keyword and is only valid for the duration of the query1.

The following are examples of how to assign an alias to a field or a database table in ABAP SQL:

B. field (from field list): A field is a column of a table or a view that contains data of a certain type. A field can be assigned an alias in the field list of a SELECT statement, which specifies the fields that are selected from the data source. For example, the following query assigns the alias name to the field carrname of the table scarr:

SELECT carrid, carrname AS name FROM scarr.

The alias name can be used instead of carrname in other clauses of the query, such as WHERE, GROUP BY, ORDER BY, and so on2.

C. database table: A database table is a collection of data that is organized in rows and columns. A database table can be assigned an alias in the FROM clause of a SELECT statement, which specifies the data source that is selected from. For example, the following query assigns the alias c to the table scarr:

SELECT c.carrid, c.carrname FROM scarr AS c.

The alias c can be used instead of scarr in other clauses of the query, such as WHERE, JOIN, GROUP BY, ORDER BY, and so on3.

The following are not valid for assigning an alias in ABAP SQL:

A. order criterion (from order by clause): An order criterion is a field or an expression that is used to sort the result set of a query in ascending or descending order. An order criterion cannot be assigned an alias in the ORDER BY clause of a SELECT statement, because the alias is not visible in this clause. The alias can only be used in the clauses that follow the clause where it is defined1.

D. group criterion (from group by clause): A group criterion is a field or an expression that is used to group the result set of a query into subsets that share the same values. A group criterion cannot be assigned an alias in the GROUP BY clause of a SELECT statement, because the alias is not visible in this clause. The alias can only be used in the clauses that follow the clause where it is defined1.

References: 1: ALIASES - ABAP Keyword Documentation 2: SELECT List - ABAP Keyword Documentation 3: FROM Clause - ABAP Keyword Documentation

The expression itab1 = corresponding #( itab2 ) is a constructor expression with the component operator CORRESPONDING that assigns the contents of the internal table itab2 to the internal table itab1. The following statements are true for using this expression:

B: itab1 and itab2 must have at least one field name in common. This is because the component operator CORRESPONDING assigns the identically named columns of itab2 to the identically named columns of itab1 by default, according to the rules of MOVE-CORRESPONDING for internal tables. If itab1 and itab2 do not have any field name in common, the expression will not assign any value to itab1 and it will remain initial or unchanged1

C: Fields with the same name and the same type will be copied from itab2 to itab1. This is because the component operator CORRESPONDING assigns the identically named columns of itab2 to the identically named columns of itab1 by default, according to the rules of MOVE-CORRESPONDING for internal tables. If the columns have the same name but different types, the assignment will try to perform a conversion between the types, which may result in a loss of precision, a truncation, or a runtime error, depending on the types involved1

The following statements are false for using this expression:

A: Fields with the same name but with different types may be copied from itab2 to itab1. This is not true, as explained in statement C. The assignment will try to perform a conversion between the types, which may result in a loss of precision, a truncation, or a runtime error, depending on the types involved1

D: itab1 and itab2 must have the same data type. This is not true, as the component operator CORRESPONDING can assign the contents of an internal table of one type to another internal table of a different type, as long as they have at least one field name in common. The target type of the expression is determined by the left-hand side of the assignment, which is itab1 in this case. The expression will create an internal table of the same type as itab1 and assign it to itab11

References: CORRESPONDING - Component Operator - ABAP Keyword Documentation

A unique secondary key is a type of secondary key that ensures that the key combination of all the rows in a table is unique. A unique secondary key has two purposes: firstly, to speed up access to the table, and secondly, to enforce data integrity1.

It is created with the first read access of a table: This is true. A unique secondary key is created when an internal table is filled for the first time using the statement READ TABLE or a similar statement. The system assigns a name and an index to each row of the table based on the key fields23.

It is updated when the modified table is read again: This is false. A unique secondary key does not need to be updated when the internal table content changes, because it already ensures data uniqueness. The system uses a lazy update strategy for non-unique secondary keys, which means that it delays updating them until they are actually accessed23.

You cannot do any of the following:

It is created when a table is filled: This is false. As explained above, a unique secondary key is created only with the first read access of a table23.

It is updated when the modified table is read again: This is false. As explained above, a unique secondary key does not need to be updated when the internal table content changes23.

References: 1: Improving Internal Table Performance Using Secondary Keys - SAP Learning 2: [Secondary Key - ABAP Keyword Documentation - SAP Online Help] 3: [Secondary Table Key - ABAP Keyword Documentation - SAP Online Help]

Using ABAP SQL, the select statement that selects the mat field on line #17 is:

SELECT mat FROM demo_sales_cds_so_i_ve…

This statement selects the mat field from the CDS view demo_sales_cds_so_i_ve, which is defined on line #1. The CDS view demo_sales_cds_so_i_ve is a projection view that projects the fields of the CDS view demo_sales_cds_so_i, which is defined on line #2. The CDS view demo_sales_cds_so_i is a join view that joins the fields of the database table demo_sales_so_i, which is defined on line #3, and the CDS view demo_sales_cds_material_ve, which is defined on line #4. The CDS view demo_sales_cds_material_ve is a value help view that provides value help for the material field of the database table demo_sales_so_i. The mat field is an alias for the material field of the database table demo_sales_so_i, which is defined on line #91.

The other options are not valid because:

A. SELECT mat FROM Material… is not valid because Material is not a valid data source in the given code. There is no CDS view or database table named Material.

C. SELECT mat FROM demo_sales_so_i… is not valid because demo_sales_so_i is not a valid data source in the given code. There is no CDS view named demo_sales_so_i, only a database table. To access a database table, the keyword TABLE must be used, such as SELECT mat FROM TABLE demo_sales_so_i…

D. SELECT mat FROM demo sales cds material ve… is not valid because demo sales cds material ve is not a valid data source in the given code. There is no CDS view or database table named demo sales cds material ve. The correct name of the CDS view is demo_sales_cds_material_ve, with underscores instead of spaces.

References: 1: Projection Views - ABAP Keyword Documentation

The data type of gv_result in the assignment data (gv_result) = 1/8 will be TYPE DECFLOAT 16. This is because the assignment operator (=) in ABAP performs an implicit type conversion from the source type to the target type, according to the following rules12:

If the target type is specified explicitly, the source value is converted to the target type.

If the target type is not specified explicitly, the source type is used as the target type, unless the source type is a literal or an expression, in which case the target type is determined by the following priority order: DECFLOAT34, DECFLOAT16, P, F, I, C, N, X, STRING, XSTRING.

In this case, the target type is not specified explicitly, and the source type is an expression (1/8). Therefore, the target type is determined by the priority order, and the first matching type is DECFLOAT16, which is a decimal floating point type with 16 digits of precision12.

References: 1: ABAP Assignment Rules - ABAP Keyword Documentation - SAP Online Help 2: ABAP Data Types - ABAP Keyword Documentation - SAP Online Help

According to the SAP clean core extensibility and ABAP cloud topic, SAP recommends using developer extensibility to enhance the existing UI for an SAP Fiori app. Developer extensibility allows you to use the UI adaptation editor in SAP Web IDE to modify the UI layout, add or remove fields, and bind them to the data model. You can also use the SAPUI5 framework to create custom controls, views, and controllers. Developer extensibility is based on the in-app extensibility concept, which means that the extensions are part of the same application and are deployed together with the app. Developer extensibility requires developer skills and access to the source code of the app. References: SAP Learning Hub, SAP S/4HANA Cloud Extensibility - In-App Extensibility, SAP Fiori: Extensibility

A projection view is a RESTful Application Programming object that contains only the fields required for a particular app. A projection view is a CDS view entity that defines a projection on an existing CDS view entity or CDS DDIC-based view. A projection view exposes a subset of the elements of the projected entity, which are relevant for a specific business service. A projection view can also define aliases, virtual elements, and annotations for the projected elements. A projection view is the top-most layer of a CDS data model and prepares data for a particular use case. A projection view can have different provider contracts depending on the type of service it supports, such as transactional query, analytical query, or transactional interface.

A database view is a CDS DDIC-based view that defines a join or union of database tables. A database view has an SQL view attached and can be accessed by Open SQL or native SQL. A database view can be used as a projected entity for a projection view, but it does not contain only the fields required for a particular app.

A metadata extension is a RESTful Application Programming object that defines additional annotations for a CDS view entity or a projection view. A metadata extension can be used to enhance the metadata of a CDS data model without changing the original definition. A metadata extension does not contain any fields, but only annotations.

A data model view is a CDS view entity that defines a data model based on database tables or other CDS view entities. A data model view can have associations, aggregations, filters, parameters, and annotations. A data model view can be used as a projected entity for a projection view, but it does not contain only the fields required for a particular app.

References: CDS Projection Views - ABAP Keyword Documentation, CDS Projection Views in ABAP CDS: What’s Your Flavor, Business Object Projection - ABAP Keyword Documentation

Field 1 (field1)

The syntax REFERENCE TO abap.cint(3) is incorrect for defining a database table field. Database table fields must be based on valid HANA-compatible data types or ABAP dictionary data types.

REFERENCE TO is used for object references in ABAP classes and is not valid in this context.

Therefore, field1 is defined incorrectly, making option C correct.

Field 2 (field2)

The data type abap.char(133) is valid for defining a character-based field in a table.

This field is correctly defined.

Field 3 (field3)

The data type abap.quan(2) is valid for defining a quantity field. The @Semantics.quantity.unitOfMeasure annotation correctly links this field to field4, which is a unit of measure field.

This field is correctly defined.

Field 4 (field4)

The data type abap.unit(2) is valid for defining a unit of measure field.

This field is correctly defined.

References:

SAP ABAP Documentation: ABAP Data Types for SAP HANA Tables

SAP Training for Back-End Developer - ABAP Cloud

The annotation that can be used to provide a short description of the data definition for developers that will be attached to the database view is the @EndUserText.label annotation. This annotation is used to specify a text label for the data definition that can be displayed in the development tools or in the documentation. The annotation can be inserted on line #27 in the code snippet provided in the question12. For example:

The following code snippet uses the @EndUserText.label annotation to provide a short description of the data definition for the CDS view ZCDS_VIEW:

@AbapCatalog.sqlViewName: ‘ZCDS_VIEW’ @AbapCatalog.compiler.compareFilter: true @AbapCatalog.preserveKey: true @AccessControl.authorizationCheck: #CHECK @EndUserText.label: ‘CDS view for flight data’ "short description for developers define view ZCDS_VIEW as select from sflight { key carrid, key connid, key fldate, seatsmax, seatsocc }

You cannot do any of the following:

@UI.headerInfo.description.label: This annotation is used to specify a text label for the description field of the header information of a UI element. This annotation is not relevant for the data definition of a database view12.

@UI.badge.title.label: This annotation is used to specify a text label for the title field of a badge UI element. This annotation is not relevant for the data definition of a database view12.

@EndUserText.quickInfo: This annotation is used to specify a quick information text for the data definition that can be displayed as a tooltip in the development tools or in the documentation. This annotation is not the same as a short description or a label for the data definition12.

References: 1: ABAP CDS - SAP Annotations - ABAP Keyword Documentation - SAP Online Help 2: ABAP CDS - Data Definitions - ABAP Keyword Documentation - SAP Online Help

Core Data Services (CDS) is a framework for defining and consuming semantically rich data models in SAP HANA. CDS supports various features that enhance the capabilities of SQL and enable developers to create data models that are optimized for performance, readability, and extensibility12. Some of the features of CDS are:

Associations: Associations are a way of defining relationships between CDS entities, such as tables or views. Associations enable navigation and path expressions in CDS queries, which allow accessing data from related entities without explicit joins. Associations also support cardinality, referential constraints, and cascading options34.

Annotations: Annotations are a way of adding metadata to CDS entities or their elements, such as fields or parameters. Annotations provide additional information or instructions for the CDS compiler, the database, or the consumers of the CDS views. Annotations can be used for various purposes, such as defining access control, UI rendering, OData exposure, or search capabilities5 .

Structured Query Language (SQL): SQL is the standard language for querying and manipulating data in relational databases. CDS is based on SQL and extends it with additional features and syntax. CDS supports SQL features such as joins, aggregations, filters, expressions, functions, and subqueries. CDS also supports SQL Script, which is a scripting language for stored procedures and functions in SAP HANA .

You cannot do any of the following:

Inheritance: Inheritance is not a feature of CDS. Inheritance is a concept in object-oriented programming that allows a class to inherit the properties and methods of another class. CDS does not support object-oriented programming or classes.

Delegation: Delegation is not a feature of CDS. Delegation is a concept in object-oriented programming that allows an object to delegate some of its responsibilities to another object. CDS does not support object-oriented programming or objects.

References: 1: Core Data Services (CDS) | CAPire 2: Core Data Services [CDS] in SAP S/4 HANA | SAP Blogs 3: Associations in Core Data Services (CDS) | SAP Help Portal 4: [CDS DDL - Association - ABAP Keyword Documentation - SAP Online Help] 5: [Annotations in Core Data Services (CDS) | SAP Help Portal] : [CDS DDL - Annotation - ABAP Keyword Documentation - SAP Online Help] : [Structured Query Language (SQL) | SAP Help Portal] : [CDS DDL - SQL Features - ABAP Keyword Documentation - SAP Online Help] : [Object-Oriented Programming in ABAP | SAP Help Portal]

 The order in which objects are created to generate a RESTful Application Programming application is A, D, C, B. This means that the following steps are followed:

First, a database table is created to store the data for the application. A database table is a CDS DDIC-based view that defines a join or union of database tables. A database table has an SQL view attached and can be accessed by Open SQL or native SQL.

Second, a data model view is created to define a data model based on the database table or other CDS view entities. A data model view is a CDS view entity that can have associations, aggregations, filters, parameters, and annotations. A data model view can also define the behavior definition and implementation for the business object.

Third, a service definition is created to define the service interface for the application. A service definition is a CDS view entity that defines a projection on a data model view or another service definition. A service definition can also define service metadata, such as service name, version, description, and annotations.

Fourth, a service binding is created to define the service binding for the application. A service binding is a CDS view entity that defines a projection on a service definition. A service binding can also define the service protocol, such as OData V2, OData V4, or REST, and the service URL.

References: CDS Data Model Views - ABAP Keyword Documentation, CDS Service Definitions - ABAP Keyword Documentation, CDS Service Bindings - ABAP Keyword Documentation, CDS Projection Views - ABAP Keyword Documentation

In RESTful Application Programming, the EML statement that retrieves an object is GET entity. The GET entity statement is used to read data of an entity instance from the database or the transaction buffer. The GET entity statement can specify the entity name, the entity key, and the entity elements to be retrieved. The GET entity statement can also use the IN LOCAL MODE addition to bypass the access control, authorization control, and feature control checks. The GET entity statement returns a single entity instance or raises an exception if no instance is found or multiple instances match the key.

The other EML statements are not used to retrieve an object, but have different purposes and effects. These statements are:

FIND entity: This statement is used to search for entity instances that match a given condition. The FIND entity statement can specify the entity name, the entity elements to be returned, and the condition to be applied. The FIND entity statement can also use the IN LOCAL MODE addition to bypass the access control, authorization control, and feature control checks. The FIND entity statement returns a table of entity instances or an empty table if no instances match the condition.

SELECT entity: This statement is used to query data of entity instances from the database or the transaction buffer. The SELECT entity statement can specify the entity name, the entity elements to be returned, and the filter, order, and aggregation options to be applied. The SELECT entity statement can also use the IN LOCAL MODE addition to bypass the access control, authorization control, and feature control checks. The SELECT entity statement returns a table of entity instances or an empty table if no instances match the query.

READ entity: This statement is not a valid EML statement, but an ABAP statement. The READ statement is used to access a single row of an internal table using the table index or the table key. The READ statement can also use the TRANSPORTING addition to specify which fields should be returned, and the INTO addition to specify the target variable. The READ statement returns a single row of the internal table or raises an exception if no row is found or multiple rows match the key.

References: GET ENTITY - ABAP Keyword Documentation, FIND ENTITY, ENTITIES - ABAP Keyword Documentation, SELECT ENTITY, ENTITIES - ABAP Keyword Documentation, READ - ABAP Keyword Documentation

Based on the following code, the variable type of connection_full is a structure. A structure is a complex data type that consists of a group of related data objects, called components, that have their own data types and names. A structure can be defined using the TYPES statement or based on an existing structure type, such as a CDS view entity or a CDS DDIC-based view. In this case, the variable connection_full is declared using the TYPE addition, which means that it has the same structure type as the CDS view entity /DMO/I_Connection. The CDS view entity /DMO/I_Connection is a data model view that defines a data model based on the database table /DMO/Connection. The CDS view entity /DMO/I_Connection has the following components: carrid, connid, airpfrom, airpto, distance, and fltime. Therefore, the variable connection_full has the same components as the CDS view entity /DMO/I_Connection, and each component has the same data type and length as the corresponding field in the database table /DMO/Connection.

References: CDS Data Model Views - ABAP Keyword Documentation, DATA - ABAP Keyword Documentation, Structure Types - ABAP Keyword Documentation

To redefine a component of a superclass in a subclass, you need to do the following12:

You add the clause REDEFINITION to the component declaration in the subclass. This indicates that the component is inherited from the superclass and needs to be reimplemented in the subclass. The redefinition must happen in the same visibility section as the component declaration in the superclass. For example, if the superclass has a public method m1, the subclass must also declare the redefined method m1 as public with the REDEFINITION clause.

You implement the redefined component in the subclass. This means that you provide the new logic or behavior for the component that is specific to the subclass. The redefined component in the subclass will override the original component in the superclass when the subclass object is used. For example, if the superclass has a method m1 that returns ‘Hello’, the subclass can redefine the method m1 to return ‘Hi’ instead.

You cannot do any of the following:

You implement the redefined component for a second time in the superclass. This is not possible, because the superclass already has an implementation for the component that is inherited by the subclass. The subclass is responsible for providing the new implementation for the redefined component, not the superclass.

You add the clause REDEFINITION to the component in the superclass. This is not necessary, because the superclass does not need to indicate that the component can be redefined by the subclass. The subclass is the one that needs to indicate that the component is redefined by adding the REDEFINITION clause to the component declaration in the subclass.

References: 1: METHODS - REDEFINITION - ABAP Keyword Documentation - SAP Online Help 2: Redefining Methods - ABAP Keyword Documentation - SAP Online Help

Secondary keys are additional keys that can be defined for internal tables to optimize the access to the table using fields that are not part of the primary key. Secondary keys can be either sorted or hashed, depending on the table type and the uniqueness of the key. Secondary keys have the following characteristics1:

A. Secondary keys must be chosen explicitly when you actually read from an internal table. This means that when you use a READ TABLE or a LOOP AT statement to access an internal table, you have to specify the secondary key that you want to use with the USING KEY addition. For example, the following statement reads an internal table itab using a secondary key sec_key:

READ TABLE itab USING KEY sec_key INTO DATA(wa).

If you do not specify the secondary key, the system will use the primary key by default2.

B. Multiple secondary keys are allowed for any kind of internal table. This means that you can define more than one secondary key for an internal table, regardless of the table type. For example, the following statement defines an internal table itab with two secondary keys sec_key_1 and sec_key_2:

DATA itab TYPE SORTED TABLE OF ty_itab WITH NON-UNIQUE KEY sec_key_1 COMPONENTS field1 field2 sec_key_2 COMPONENTS field3 field4.

You can then choose which secondary key to use when you access the internal table1.

D. Sorted secondary keys do NOT have to be unique. This means that you can define a sorted secondary key for an internal table that allows duplicate values for the key fields. A sorted secondary key maintains a predefined sorting order for the internal table, which is defined by the key fields in the order in which they are specified. For example, the following statement defines a sorted secondary key sec_key for an internal table itab that sorts the table by field1 in ascending order and field2 in descending order:

DATA itab TYPE STANDARD TABLE OF ty_itab WITH NON-UNIQUE SORTED KEY sec_key COMPONENTS field1 ASCENDING field2 DESCENDING.

You can then access the internal table using the sorted secondary key with a binary search algorithm, which is faster than a linear search3.

The following are not characteristics of secondary keys for internal tables, because:

C. Hashed secondary keys do NOT have to be unique. This is false because hashed secondary keys must be unique. This means that you can only define a hashed secondary key for an internal table that does not allow duplicate values for the key fields. A hashed secondary key does not have a predefined sorting order for the internal table, but uses a hash algorithm to store and access the table rows. For example, the following statement defines a hashed secondary key sec_key for an internal table itab that hashes the table by field1 and field2:

DATA itab TYPE STANDARD TABLE OF ty_itab WITH UNIQUE HASHED KEY sec_key COMPONENTS field1 field2.

You can then access the internal table using the hashed secondary key with a direct access algorithm, which is very fast.

E. Secondary keys can only be created for standard tables. This is false because secondary keys can be created for any kind of internal table, such as standard tables, sorted tables, and hashed tables. However, the type of the secondary key depends on the type of the internal table. For example, a standard table can have sorted or hashed secondary keys, a sorted table can have sorted secondary keys, and a hashed table can have hashed secondary keys1.

References: 1: Secondary Table Key - ABAP Keyword Documentation 2: READ TABLE - ABAP Keyword Documentation 3: Sorted Tables - ABAP Keyword Documentation : Hashed Tables - ABAP Keyword Documentation