Feature Matrix: Data Modeling with ABAP Core Data Services

Contents:

1. CDS entities
2. CDS user-defined types
3. CDS user-defined functions
4. CDS associations (regular, compositions, and to-parent)
5. Joins
6. Clauses
7. Operands and expressions
   1. Operands
      1. Typed literal
      2. Untyped literal
      3. Field
      4. Parameter
      5. Session variable
   2. Expressions
      1. Arithmetic expression
      2. Aggregate function
      3. Case distinction (simple and complex)
      4. Cast expression (including new casts since release 7.55)
      5. Reusing expressions from the SELECT list with $projection 
      6. Relational operators
      7. Path expressions
      8. Amounts and quantities in expressions
   3. Built-in functions
      1. Numeric functions
      2. String functions
      3. Coalesce function
      4. Conversion functions (type conversion, unit and currency conversion, date and time conversion)
8. CDS system entities
9. CDS tuning objects
10. CDS entity extensions
11. Development pipeline
12. Documentation resources
13. ABAP Learning Resources

1. CDS entities

The following CDS entities are available in release ABAP Platform 2022 for data modeling.

Note: Column Release lists three release numbers. The first one refers to the ABAP release, the second one to the kernel release and the third one to the ABAP Platform Classic release.

Did you know?

• Check our Data Source Matrix to learn how to combine data sources in CDS: Data sources after FROM and association targets.
• CDS entities are like chameleons: even after you’ve activated and transported an entity, you can change the type of your CDS entity. For example, you have a CDS view and want to convert it into a custom entity for specialization. Or you want to convert an abstract entity into a view to have more options. As long as the consumers are not affected, just change the syntax and activate and transport the changed object.

2. CDS user-defined types

@EndUserText.label: 'This is a simple type'
define type myType : abap.char(5);

@EndUserText.label: 'CDS enum type with base type char'
define type DEMO_CDS_ENUM_CHAR : abap.char(1) enum
{
  initial_value = initial;
  first_value   = 'A';
  second_value  = 'B';
}

3. CDS user-defined functions

SQL-based scalar functions

An SQL-based scalar function is a user-defined function that accepts multiple input parameters and returns exactly one scalar value. A scalar function allows developers to encapsulate complex algorithms into manageable, reusable code that can then be used in all operand positions of CDS view entities that expect scalar values. A scalar function is linked with an AMDP function in which it is implemented using SQLScript.

A SQL-based scalar function consists of three repository objects:

• CDS scalar function definition defined in ABAP CDS using DEFINE SCALAR FUNCTION.
• A CDS scalar function implementation reference that binds the scalar function to a runtime engine and to an AMDP function implementation.
• An AMDP method that implements the CDS scalar function as database function in SQLScript.

Example:

CDS scalar function definition:

define scalar function DEMO_CDS_SCALAR_RATIO
  with parameters
    portion: numeric
    total  : type of portion
  returns abap.decfloat34;

CDS scalar function implementation reference:

AMDP function implementation:

  METHOD execute BY DATABASE FUNCTION
                 FOR HDB
                 LANGUAGE SQLSCRIPT
                 OPTIONS READ-ONLY.
    result = portion / total * 100;
  ENDMETHOD.

• Available since ABAP release 7.93
• ABAP Keyword Documentation: CDS SQL-based scalar functions
• ABAP Data Models Guide, Scalar Functions | SAP Help Portal
• Blog Post: ABAP CDS Release News 2308 – CDS Scalar Functions Implemented by AMDP | SAP Blogs

4. CDS associations

Associations describe the relationships between CDS entities. They define a join that is instantiated only when fields are retrieved from the associated entity.

Use cases of CDS associations and how they are transformed into joins are documented here. Moreover, there’s a blog post: From Open SQL Joins to CDS Associations | SAP Blogs.

Types of associations:

Regular, not specialized CDS association

• Available since ABAP release 7.4 SP5.
• Available in CDS view entities, CDS projection views, CDS custom entities, CDS abstract entities, and CDS DDIC-based views.
• Docu
• Syntax:

ASSOCIATION [ OF {EXACT ONE | MANY | ONE} TO {EXACT ONE | MANY | ONE} ] 
  TO target [AS _assoc] 
  ON cds_cond 
  [ WITH DEFAULT FILTER cds_cond ]

CDS composition

• Specialized CDS association that defines the current entity as parent and the composition target as child.
• Available since ABAP release 7.75, ABAP Platform Classic 1809 SP01.
• Available in CDS view entities, CDS projection views, CDS custom entities, CDS abstract entities, and CDS DDIC-based views.
• Docu
• Syntax:

COMPOSITION [ OF {EXACT ONE | MANY | ONE} 
              TO {EXACT ONE | MANY | ONE} ] 
  target [AS _compos]

Association to parent

• Specialized CDS association that defines the current entity as child and the association target as parent. The child depends on the parent and cannot exist without the parent. For example, a sales order item (composition child) always belongs to a sales order header (composition parent).
• Available since ABAP release 7.75, ABAP Platform Classic 1809 SP01.
• Available in CDS view entities, CDS projection views, CDS custom entities, CDS abstract entities, and CDS DDIC-based views.
• Docu
• Syntax:

ASSOCIATION TO PARENT target [AS _assoc] ON $projection.cds_cond

5. Joins

In ABAP CDS, the following join types are available for modeling relationships between CDS entities:

6. Clauses

Note: Column Release lists three release numbers. The first one refers to the ABAP release, the second one to the kernel release and the third one to the SAP BTP ABAP Environment release.

7. Operands and expressions

7.1 Operands

Note: Column Release lists three release numbers. The first one refers to the ABAP release, the second one to the kernel release and the third one to the SAP BTP ABAP Environment release.

7.2 Expressions

Arithmetic expressions

• Available since ABAP release 7.4 SP5
• Docu

Aggregate functions

• Available since ABAP release 7.4 SP5
• Docu

Case distinction

• Simple case is available since ABAP release 7.4 SP5
• Searched case is available since 7.4 SP8
• New in release kernel release 7.89 | ABAP release 7.57 | SAP BTP ABAP Environment 2208: THEN ELSE NULL is available to explicitly define the null value as return value if no matches are found.
• Docu

A case expression in ABAP CDS always returns exactly one value, depending on the conditions. The simple case expression compares an expression to several other expressions for equality:

CASE operand 
           WHEN operand1 THEN result1 
          [WHEN operand2 THEN result2] 
           ... 
          [{ELSE resultn | ELSE NULL}] 
      END

The complex case expression (aka ‘searched case’) evaluates N independent conditions. The first case to be evaluated to TRUE returns the result. If none of the conditions are true, the result is determined by the ELSE branch:

CASE WHEN cds_cond1 THEN result1 
        [WHEN cds_cond2 THEN result2] 
        [WHEN cds_cond3 THEN result3] 
          ... 
        [{ELSE resultn | ELSE NULL}] 
    END

Cast expression

• Data type conversion
• Available since ABAP release 7.4 SP5, but the cast matrix has been extended over time.
• Docu (including full cast matrix)
• Syntax:

• CAST( <expression> AS <datatype> [PRESERVING TYPE])

• New casts since ABAP release 7.55

• FROM	TO
  SSTRING	DEC, CURR, QUAN, INT1, INT2, INT4, INT8, DECFLOAT16, and DECFLOAT34
  CHAR	DEC, CURR, QUAN, INT1, INT2, INT4, INT8, DECFLOAT16, and DECFLOAT34
  DATS	DEC, CURR, QUAN, INT1, INT2, INT4, INT8, DECFLOAT16, and DECFLOAT34
  TIMS	DEC, CURR, QUAN, INT1, INT2, INT4, INT8, DECFLOAT16, and DECFLOAT34
  DECFLOAT16	CHAR
  DECFLOAT34	CHAR
  FLTP	DEC, CURR, QUAN, INT1, INT2, INT4, INT8, DECFLOAT16, and DECFLOAT34

Reusing expressions from the SELECT list

• $projection.elementName reuses an expression from the SELECT list in another operand position of the same CDS entity. This enables further processing of calculated fields and avoids the workaround of building a view stack for that purpose.
• Available since ABAP release 7.56 | kernel release 7.84 | SAP BTP ABAP Environment 2105
• Docu
• Example:

• define view entity DEMO_CDS_EXPRESSION_REUSE 
    as select from demo_expressions 
  { 
        //arithmetic expression 
        abap.decfloat34'123.45E6'              as arith, 
        $projection.arith * 2                  as arith_reuse, 
  
        //cast expression 
        cast(char1 as abap.numc(10))           as cast1, 
        coalesce($projection.cast1, numc2)     as cast_reuse, 
  
        //built-in function 
        abs(dec1)                              as builtIn, 
        cast($projection.builtIn as abap.int4) as builtIn_reuse, 
  }
  

Relational operators

Path expressions

Path expressions can be used to include fields from associated sources in the field list of the CDS entity. A path expression can also go over several levels. It is also possible to add attributes to the evaluation of the associations, for example to filter or to define the join type.

Example:

_Items[1:currency <> 'EUR'].material = 'WOOD' 

Amounts and quantities in expressions

Amount and quantity handling in expressions in ABAP CDS has been overhauled since ABAP release 7.56 | kernel release 7.84 | SAP BTP ABAP Environment 2105. See the following blog post for details: ABAP CDS Cheat Sheet: Amounts and Quantities in ABAP CDS | SAP Blogs.

7.3 Built-in functions

Numeric functions 

• Docu

String functions

• Docu

Coalesce function

The coalesce function checks for null values.

Syntax:

COALESCE( arg1, arg2 )

 case cast( _a.char1 as char3)
          when substring( cast( 'AA' as char2), $parameters.p1, 2*2)  then 'text1'
          when case 'a' when 'b' then 'c' end                         then 'text2'
          else NULL
          end                 as CaseExp

8. CDS system entities

FINAL(current_date) = sy-datum.
FINAL(one_year_later) = current_date + 365.

SELECT * FROM series_generate_date( step       = 30,
                                    from_value = @current_date,
                                    to_value   = @one_year_later )
  ORDER BY element_number
  INTO TABLE @FINAL(date_series_gen).

cl_demo_output=>display( date_series_gen ).