C_ABAPD_2309 SAP Certified Associate - Back-End Developer - ABAP Cloud Questions and Answers

Use public SAP APIs and SAP extension points. This rule ensures that the ABAP Cloud code is stable, reliable, and compatible with the SAP solutions and the cloud operations. Public SAP APIs and SAP extension points are the only allowed interfaces and objects to access the SAP platform and the SAP applications. They are documented, tested, and supported by SAP. They also guarantee the lifecycle stability and the upgradeability of the ABAP Cloud code1.

Build ABAP RESTful application programming model-based services. This rule ensures that the ABAP Cloud code follows the state-of-the-art development paradigm for building cloud-ready business services. The ABAP RESTful application programming model (RAP) is a framework that provides a consistent end-to-end programming model for creating, reading, updating, and deleting (CRUD) business data. RAP also supports draft handling, authorization checks, side effects, validations, and custom actions. RAP exposes the business services as OData services that can be consumed by SAP Fiori apps or other clients2.

The access to internal tables can be optimized by using the appropriate table type and specifying the table key. The table key is a set of fields that uniquely identifies a row in the table and determines the sorting order of the table. The table key can be either the primary key or a secondary key. The primary key is defined by the table type and the table definition, while the secondary key is defined by the user using the KEY statement1.

The following results in faster access to internal tables:

B. In a sorted internal table, specifying the primary key completely. A sorted internal table is a table type that maintains a predefined sorting order, which is defined by the primary key in the table definition. The primary key can be either unique or non-unique. A sorted internal table can be accessed using the primary key or the table index. The access using the primary key is faster than the access using the table index, because the system can use a binary search algorithm to find the row. However, the primary key must be specified completely, meaning that all the fields of the primary key must be given in the correct order and without gaps2.

D. In a hashed internal table, specifying the primary key partially from the left without gaps. A hashed internal table is a table type that does not have a predefined sorting order, but uses a hash algorithm to store and access the rows. The primary key of a hashed internal table must be unique and cannot be changed. A hashed internal table can only be accessed using the primary key, not the table index. The access using the primary key is very fast, because the system can directly calculate the position of the row using the hash algorithm. The primary key can be specified partially from the left without gaps, meaning that some of the fields of the primary key can be omitted, as long as they are the rightmost fields and there are no gaps between the specified fields.

E. In a hashed internal table, specifying the primary key completely. A hashed internal table is a table type that does not have a predefined sorting order, but uses a hash algorithm to store and access the rows. The primary key of a hashed internal table must be unique and cannot be changed. A hashed internal table can only be accessed using the primary key, not the table index. The access using the primary key is very fast, because the system can directly calculate the position of the row using the hash algorithm. The primary key can be specified completely, meaning that all the fields of the primary key must be given in the correct order.

The following do not result in faster access to internal tables, because:

A. In a sorted internal table, specifying the primary key partially from the left without gaps. A sorted internal table is a table type that maintains a predefined sorting order, which is defined by the primary key in the table definition. The primary key can be either unique or non-unique. A sorted internal table can be accessed using the primary key or the table index. The access using the primary key is faster than the access using the table index, because the system can use a binary search algorithm to find the row. However, the primary key must be specified completely, meaning that all the fields of the primary key must be given in the correct order and without gaps. If the primary key is specified partially from the left without gaps, the system cannot use the binary search algorithm and has to perform a linear search, which is slower2.

C. In a standard internal table, specifying the primary key partially from the left without gaps. A standard internal table is a table type that does not have a predefined sorting order, but uses a sequential storage and access of the rows. The primary key of a standard internal table is the standard key, which consists of all the fields of the table row in the order in which they are defined. A standard internal table can be accessed using the primary key or the table index. The access using the primary key is slower than the access using the table index, because the system has to perform a linear search to find the row. The primary key can be specified partially from the left without gaps, but this does not improve the access speed, because the system still has to perform a linear search.

References: 1: Internal Tables - Overview - ABAP Keyword Documentation 2: Sorted Tables - ABAP Keyword Documentation : Hashed Tables - ABAP Keyword Documentation : Standard Tables - ABAP Keyword Documentation

An Access Control Object (ACO) is a CDS annotation that defines the access control rules for a CDS view entity. An ACO consists of one or more clauses that specify the role name, the data source, the access conditions, and the return code of the authority check12. Some of the clauses that are used in an ACO are:

Where (to specify the access conditions): This clause is used to define the logical expression that determines whether a user has access to the data source or not. The expression can use the fields of the data source, the parameters of the CDS view entity, or the predefined variables $user and $session. The expression can also use the functions check_authorization and check_role to perform additional authority checks12.

Define role (to specify the role name): This clause is used to assign a name to the role that is defined by the ACO. The role name must be unique within the namespace of the CDS view entity and must not contain any special characters. The role name can be used to reference the ACO in other annotations, such as @AccessControl.authorizationCheck or @AccessControl.grant12.

Revoke (to remove access to the data source): This clause is used to explicitly deny access to the data source for a user who meets the conditions of the where clause. The revoke clause overrides any grant clause that might grant access to the same user. The revoke clause can be used to implement the principle of least privilege or to enforce data segregation12.

You cannot do any of the following:

Grant (to identify the data source): This is not a valid clause in an ACO. The grant clause is a separate annotation that is used to grant access to a CDS view entity or a data source for a user who has a specific role. The grant clause can reference an ACO by its role name to apply the access conditions defined by the ACO12.

Return code (to assign the return code of the authority check): This is not a valid clause in an ACO. The return code of the authority check is a predefined variable that is set by the system after performing the access control check. The return code can be used in the where clause of the ACO to specify different access conditions based on the outcome of the check12.

References: 1: Access Control Objects - ABAP Keyword Documentation - SAP Online Help 2: Access Control in Core Data Services (CDS) | SAP Help Portal

In a RESTful Application Programming (RAP) application, you can bind a CDS view to create a value help in the following objects:

Data model view: A data model view is a CDS view that defines the data structure and the associations of an entity in the RAP application. You can use the annotation @Consumption.valueHelpDefinition to bind a value help provider CDS view to an element of the data model view. The value help provider CDS view must contain the key fields of the value help entity and the fields that are displayed in the value help dialog. The value help annotation specifies the entity name, the element name, and optionally the additional binding conditions for the value help provider1.

Metadata Extension: A metadata extension is a CDS view that extends the metadata of another CDS view without changing its data structure. You can use the annotation @MetadataExtension.extendView to specify the target CDS view that you want to extend. You can then use the same annotation @Consumption.valueHelpDefinition to bind a value help provider CDS view to an element of the target CDS view. The metadata extension allows you to add value help definitions to existing CDS views without modifying them2.

Projection View: A projection view is a CDS view that defines the projection of another CDS view. You can use the annotation @AbapCatalog.sqlViewType: #PROJECTION to specify that the CDS view is a projection view. You can then use the same annotation @Consumption.valueHelpDefinition to bind a value help provider CDS view to an element of the projection view. The projection view allows you to add value help definitions to projected elements of another CDS view3.

You cannot bind a value help provider CDS view to a behavior definition or a service definition, because these objects do not define the data structure or the metadata of an entity in the RAP application. A behavior definition defines the behavior and the validation rules of an entity, such as the create, read, update, and delete (CRUD) operations, the draft handling, the authorization checks, and the side effects4. A service definition defines the service exposure and the service binding of an entity, such as the protocol, the version, the namespace, and the service name5.

References: 1: Value Help with Additional Binding | SAP Help Portal 2: Metadata Extensions - ABAP Keyword Documentation 3: Projection Views - ABAP Keyword Documentation 4: Behavior Definition - ABAP Keyword Documentation 5: Service Definition - ABAP Keyword Documentation

The annotation @Environment.systemField: #LANGUAGE is used to assign the ABAP system field sy-langu to an input parameter of a CDS view or a CDS table function. This enables the implicit parameter passing in Open SQL, which means that the value of sy-langu will be automatically passed to the CDS view without explicitly specifying it in the WHERE clause. This also applies to the CDS views that use the annotated CDS view as a data source, which means that the value of sy-langu will be propagated to the nested CDS views (view on view)12. For example:

The following code snippet defines a CDS view ZI_FLIGHT_TEXTS with an input parameter p_langu that is annotated with @Environment.systemField: #LANGUAGE:

define view ZI_FLIGHT_TEXTS with parameters p_langu : syst_langu @

The following code snippet shows how to use the CDS view ZI_FLIGHT_TEXTS in ABAP without specifying the value of p_langu in the WHERE clause. The value of sy-langu will be automatically passed to the CDS view:

SELECT carrid, connid, fldate, carrname, carrtext FROM zi_flight_texts INTO TABLE @DATA(lt_flights).

The following code snippet shows how to use the CDS view ZI_FLIGHT_TEXTS in another CDS view ZI_FLIGHT_REPORT. The value of sy-langu will be automatically passed to the nested CDS view ZI_FLIGHT_TEXTS:

define view ZI_FLIGHT_REPORT with parameters p_langu : syst_langu @

The annotation @Environment.systemField: #LANGUAGE does not prevent the possibility of overriding the default value with a value of your own. You can still specify a different value for the input parameter p_langu in the WHERE clause, either in ABAP or in another CDS view. This will override the value of sy-langu and pass the specified value to the CDS view12. For example:

The following code snippet shows how to use the CDS view ZI_FLIGHT_TEXTS in ABAP with a specified value of p_langu in the WHERE clause. The value ‘E’ will be passed to the CDS view instead of the value of sy-langu:

SELECT carrid, connid, fldate, carrname, carrtext FROM zi_flight_texts WHERE p_langu = ‘E’ INTO TABLE @DATA(lt_flights).

The following code snippet shows how to use the CDS view ZI_FLIGHT_TEXTS in another CDS view ZI_FLIGHT_REPORT with a specified value of p_langu in the WHERE clause. The value ‘E’ will be passed to the nested CDS view ZI_FLIGHT_TEXTS instead of the value of sy-langu:

define view ZI_FLIGHT_REPORT with parameters p_langu : syst_langu @

References: 1: ABAP CDS - parameter_annot - ABAP Keyword Documentation - SAP Online Help 2: ABAP CDS - session_variable - ABAP Keyword Documentation - SAP Online Help

When processing a loop with the statement DO… ENDDO, the system variable that contains the implicit loop counter is sy-index. The loop counter is a numeric value that indicates how many times the loop has been executed. The loop counter is initialized to 1 before the first execution of the loop and is incremented by 1 after each execution. The loop counter can be used to control the number of loop iterations or to access the loop elements by index. The loop counter can also be accessed or modified within the loop body, but this is not recommended as it may cause unexpected results or errors1.

For example, the following code snippet uses the loop counter sy-index to display the numbers from 1 to 10:

DO 10 TIMES. WRITE: / sy-index. ENDDO.

The output of this code is:

1 2 3 4 5 6 7 8 9 10

References: 1: DO - ABAP Keyword Documentation

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 nested join is evaluated from the top to the bottom in the order of the ON conditions. This means that the join expression is formed by assigning each ON condition to the directly preceding JOIN from left to right. The join expression can be parenthesized implicitly or explicitly to show the order of evaluation. In this case, the implicit parentheses are as follows:

SELECT * FROM (a INNER JOIN (b INNER JOIN c ON b~c = c~c) ON a~b = b~b)

This means that the first join expression is b INNER JOIN c ON b~c = c~c, which joins the columns of tables b and c based on the condition that b~c equals c~c. The second join expression is a INNER JOIN (b INNER JOIN c ON b~c = c~c) ON a~b = b~b, which joins the columns of table a and the result of the first join expression based on the condition that a~b equals b~b. The final result set contains all combinations of rows from tables a, b, and c that satisfy both join conditions.

References: 1: SELECT, FROM JOIN - ABAP Keyword Documentation - SAP Online Help

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

The RESTful Application Programming feature that is used to ensure the uniqueness of a semantic key is determination. A determination is a type of behavior implementation that defines a logic that is executed automatically when certain events occur, such as create, update, delete, or activate. A determination can be used to calculate or derive values for certain fields, such as semantic keys, based on other fields or external sources. A determination can also be used to check the uniqueness of a semantic key by comparing it with the existing values in the database or the transaction buffer. A determination can use the ABAP SQL or the EML syntax to access and manipulate data. A determination can be defined using the DETERMINE action clause in the behavior definition of a CDS view entity or a projection view. A determination can also be annotated with the @ObjectModel.determination annotation to specify the event, the timing, and the scope of the determination12

The other RESTful Application Programming features are not used to ensure the uniqueness of a semantic key, but have different purposes and effects. These features are:

Validation: A validation is a type of behavior implementation that defines a logic that is executed automatically when certain events occur, such as create, update, delete, or activate. A validation can be used to check the consistency and correctness of the data, such as mandatory fields, data types, value ranges, or business rules. A validation can use the ABAP SQL or the EML syntax to access and manipulate data. A validation can be defined using the VALIDATE action clause in the behavior definition of a CDS view entity or a projection view. A validation can also be annotated with the @ObjectModel.validation annotation to specify the event, the timing, and the scope of the validation12

Action: An action is a type of behavior implementation that defines a logic that is executed explicitly by the user or the application. An action can be used to perform a specific business operation, such as creating, updating, deleting, or activating an entity instance, or triggering a workflow or a notification. An action can use the ABAP SQL or the EML syntax to access and manipulate data. An action can be defined using the ACTION clause in the behavior definition of a CDS view entity or a projection view. An action can also be annotated with the @ObjectModel.action annotation to specify the name, the description, the parameters, and the visibility of the action12

References: Behavior Implementation - ABAP Keyword Documentation, Behavior Definition - ABAP Keyword Documentation

 In class ZCL_CLASS_A, you use the statement DATA var TYPE *** to declare a data object named var with a data type specified by ***. The data type can be any of the following1:

A predefined ABAP type, such as i, f, c, string, xstring, and so on.

A data element from the ABAP Dictionary, such as matnr, carrid, bukrs, and so on. A data element defines the semantic and technical attributes of a data field, such as the domain, the length, the data type, the description, and the value range2.

A domain from the ABAP Dictionary, such as matnr_d, carrid_d, bukrs_d, and so on. A domain defines the technical attributes of a data field, such as the data type, the length, the output length, the number of decimal places, and the value range3.

A type defined globally in a class, an interface, or a type pool, such as zcl_class_b=>type_a, zif_interface_c=>type_b, ztype_pool_d=>type_c, and so on. A global type is a type that is defined in a global repository object and can be used in any program or class4.

A type defined locally in the current class, such as type_a, type_b, type_c, and so on. A local type is a type that is defined in the declaration part of a class and can only be used within the class5.

Therefore, the possible values for *** are B. the name of a data element from the ABAP Dictionary and D. the name of a domain from the ABAP Dictionary. The other options are not valid because:

A. The name of a type defined privately in class ZCL_CLASS_A is a local type and cannot be used with the DATA statement. A local type can only be used with the TYPES statement5.

C. The name of a type defined privately in another class is a private type and cannot be accessed from outside the class. A private type can only be used within the class that defines it.

References: 1: DATA - ABAP Keyword Documentation 2: Data Elements - ABAP Dictionary - SAP Online Help 3: Domains - ABAP Dictionary - SAP Online Help 4: Global Types - ABAP Keyword Documentation 5: Local Types - ABAP Keyword Documentation : Private Types - ABAP Keyword Documentation

The predicate condition that can be used to ensure that the CAST will work is IS INSTANCE OF. The IS INSTANCE OF predicate condition checks whether the operand is an instance of the specified class or interface. This is useful when you want to perform a downcast, which is a conversion from a more general type to a more specific type. A downcast can fail if the operand is not an instance of the target type, and this can cause a runtime error. Therefore, you can use the IS INSTANCE OF predicate condition to check whether the downcast is possible before using the CAST operator12. For example:

The following code snippet uses the IS INSTANCE OF predicate condition to check whether the variable g_super is an instance of the class lcl_super. If it is, the CAST will work and the variable g_sub1 will be assigned the value of g_super.

DATA: g_super TYPE REF TO lcl_super, g_sub1 TYPE REF TO lcl_sub1. IF g_super IS INSTANCE OF lcl_super. g_sub1 = CAST #( g_super ). g_sub1->method( … ). ENDIF.

You cannot do any of the following:

IS SUPPLIED: The IS SUPPLIED predicate condition checks whether an optional parameter of a method or a function module has been supplied by the caller. This is useful when you want to handle different cases depending on whether the parameter has a value or not. However, this predicate condition has nothing to do with the CAST operator or the type of the operand12.

IS NOT INITIAL: The IS NOT INITIAL predicate condition checks whether the operand has a non-initial value. This is useful when you want to check whether the operand has been assigned a value or not. However, this predicate condition does not guarantee that the CAST will work, because the operand may have a value but not be an instance of the target type12.

IS BOUND: The IS BOUND predicate condition checks whether the operand is a bound reference variable. This is useful when you want to check whether the operand points to an existing object or not. However, this predicate condition does not guarantee that the CAST will work, because the operand may point to an object but not be an instance of the target type12.

References: 1: Predicate Expressions - ABAP Keyword Documentation - SAP Online Help 2: ABAP - Predicates | SAP Community

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

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 following are the explanations for each statement:

A: This statement is valid. go_ifl may call method ml with go_ifl->ml(). This is because go_ifl is a data object of type REF TO ifl, which is a reference to the interface ifl. The interface ifl defines a method ml, which can be called using the reference variable go_ifl. The class cll implements the interface ifl, which means that it provides an implementation of the method ml. The data object go_ifl is assigned to a new instance of the class cll using the NEW operator and the inline declaration operator @DATA. Therefore, when go_ifl->ml() is called, the implementation of the method ml in the class cll is executed123

B: This statement is valid. Instead of go_cll = NEW #(…) you could use go_ifl = NEW cll(…). This is because go_ifl is a data object of type REF TO ifl, which is a reference to the interface ifl. The class cll implements the interface ifl, which means that it is compatible with the interface ifl. Therefore, go_ifl can be assigned to a new instance of the class cll using the NEW operator and the class name cll. The inline declaration operator @DATA is optional in this case, as go_ifl is already declared. The parentheses after the class name cll can be used to pass parameters to the constructor of the class cll, if any123

E: This statement is valid. go_ifl may call method m2 with go_ifl->m2(…). This is because go_ifl is a data object of type REF TO ifl, which is a reference to the interface ifl. The class cll implements the interface ifl, which means that it inherits all the components of the interface ifl. The class cll also defines a method m2, which is a public method of the class cll. Therefore, go_ifl can call the method m2 using the reference variable go_ifl. The method m2 is not defined in the interface ifl, but it is accessible through the interface ifl, as the interface ifl is implemented by the class cll. The parentheses after the method name m2 can be used to pass parameters to the method m2, if any123

The other statements are not valid, as they have syntax errors or logical errors. These statements are:

C: This statement is not valid. go_cll may call method ml with go_cll->ifl~ml(). This is because go_cll is a data object of type REF TO cll, which is a reference to the class cll. The class cll implements the interface ifl, which means that it inherits all the components of the interface ifl. The interface ifl defines a method ml, which can be called using the reference variable go_cll. However, the syntax for calling an interface method using a class reference is go_cll->ml(), not go_cll->ifl~ml(). The interface component selector ~ is only used when calling an interface method using an interface reference, such as go_ifl->ifl~ml(). Using the interface component selector ~ with a class reference will cause a syntax error123

D: This statement is not valid. Instead of go_cll = NEW #() you could use go_ifl = NEW #(…). This is because go_ifl is a data object of type REF TO ifl, which is a reference to the interface ifl. The interface ifl cannot be instantiated, as it does not have an implementation. Therefore, go_ifl cannot be assigned to a new instance of the interface ifl using the NEW operator and the inline declaration operator @DATA. This will cause a syntax error or a runtime error. To instantiate an interface, you need to use a class that implements the interface, such as the class cll123

References: INTERFACES - ABAP Keyword Documentation, CLASS - ABAP Keyword Documentation, NEW - ABAP Keyword Documentation

The internal table type that allows both unique and non-unique keys is the standard table. A standard table has an internal linear index that can be used to access the table entries. The key of a standard table is always non-unique, which means that the table can contain duplicate entries. However, the system does not check the uniqueness of the key when inserting new entries, so the programmer can ensure that the key is unique by using appropriate logic. A standard table can be accessed either by using the table index or the key, but the response time for key access is proportional to the table size.

The other two internal table types, sorted and hashed, do not allow non-unique keys. A sorted table is filled in sorted order according to the defined table key, which must be unique. A sorted table can be accessed either by using the table index or the key, but the response time for key access is logarithmically proportional to the table size. A hashed table can only be accessed by using a unique key, which must be specified when declaring the table. A hashed table has no index, and the response time for key access is constant, regardless of the table size.

References: Internal Tables - ABAP Keyword Documentation, SAP ABAP: Types Of Internal Table Declaration - dan852.com

In ABAP SQL, the syntax to retrieve the association field of a CDS view is to use the @ sign followed by the association name and the field name, separated by a period sign (.). For example, to retrieve the association field _Airline-Name of a CDS view, the syntax is @_Airline.Name. This syntax allows the access to the fields of the target data source of the association without explicitly joining the data sources1. The other options are incorrect because they use the wrong symbols or formats to access the association field.

References: 1: Path Expressions - ABAP Keyword Documentation