Today we delve into advanced ABAP structuring concepts.

We will clearly understand:

1. Type Groups (Type Pools)

2. Class Types (OO ABAP)

3. Implementing Views using ABAP JOIN code

This topic is crucial for clean coding, reusable design, and real-time development projects.

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🔹 PART 1: TYPE GROUP (TYPE POOL)

What is a Type Group?

A Type Group (also called Type Pool) is a container that holds globally reusable type definitions and constants.

Think of it like:

📦 A shared toolbox that stores structures, table types, and constants under one common name.

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Why Use a Type Group?

• To define global reusable types

• To maintain centralized type definitions

• To improve readability

• To standardize structures across programs

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Where is a Type Group Created?

• T-Code: SE11

• Object Type: Type Group

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How to Use a Type Group in a Program?

To use a Type Group, include it in your program with the TYPE-POOLS statement. This makes all types defined inside the Type Group available for use.

Example:

TYPE-POOLS: ZSD_TYPES.

Now all types defined inside ZSD_TYPES can be used.

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Naming Convention

All types inside a Type Group must start with the type group name.

Example:

If Type Group = ZSD_TYPES

Then type should be:

TYPES: BEGIN OF ZSD_TYPES_STRUCTURE,
         field1 TYPE c LENGTH 10,
         field2 TYPE i,
       END OF ZSD_TYPES_STRUCTURE.

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Advantages

✔ Reusable across multiple programs
✔ Clean structured development
✔ Centralized control

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Disadvantages

❌ Entire type group loads into memory
❌ In modern ABAP, Global Classes are preferred

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🔹 Practical Example: Custom Types in Program

Below is a clean structured version of your example:

TYPES: BEGIN OF ty_student,
         id TYPE i,
         name TYPE c LENGTH 50,
       END OF ty_student.

DATA: lt_students TYPE TABLE OF ty_student,
      ls_student TYPE ty_student.

SELECT id name FROM zdt_student INTO TABLE lt_students.

LOOP AT lt_students INTO ls_student.
  WRITE: / ls_student-id, ls_student-name.
ENDLOOP.

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What is Happening Here?

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🔹 PART 2: CLASS TYPES (Object-Oriented ABAP)

Now we move to modern ABAP – Object-Oriented Programming (OOP).

In real projects, Classes are preferred over Type Groups.

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What is a Class in ABAP?

A Class is:

A blueprint that contains data and methods (logic) together.

Created using:

• T-Code: SE24

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Basic Class Template

CLASS lcl_example DEFINITION.
  PUBLIC SECTION.
    METHODS: display.
ENDCLASS.

CLASS lcl_example IMPLEMENTATION.
  METHOD display.
    WRITE: 'Hello, ABAP OOP!'.
  ENDMETHOD.
ENDCLASS.

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Calling a Class in a Program

DATA: lo_example TYPE REF TO lcl_example.

CREATE OBJECT lo_example.
CALL METHOD lo_example->display.

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🔹 PART 3: IMPLEMENTING VIEW LOGIC USING ABAP JOIN

Now we will simulate what a Database View does using ABAP JOIN.

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Scenario:

We have two tables:

• ZDT_STUDENT_HDR (Header)

• ZDT_STUDENT_ITEM (Item)

We want combined data.

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Clean Production-Style ABAP JOIN Code

SELECT-OPTIONS: s_id FOR zdt_student_hdr-id.

SELECT a~id a~name b~subject
  INTO TABLE @DATA(lt_combined)
  FROM zdt_student_hdr AS a
  INNER JOIN zdt_student_item AS b
  ON a~id = b~student_id
  WHERE a~id IN @s_id.

LOOP AT lt_combined INTO DATA(ls_combined).
  WRITE: / ls_combined-id, ls_combined-name, ls_combined-subject.
ENDLOOP.

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What is Happening Here?

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🔹 Important Difference

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🔹 Modern Better Version (New ABAP Syntax)

SELECT a~id, a~name, b~subject
  FROM zdt_student_hdr AS a
  INNER JOIN zdt_student_item AS b
  ON a~id = b~student_id
  INTO TABLE @DATA(lt_combined)
  WHERE a~id IN @s_id.

Modern ABAP:

• Uses @

• Inline declarations

• Cleaner and safer

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🔹 Quick Memory Chart

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🔥 Final Understanding

• Type Group = Old structured reusable types

• Classes = Modern reusable logic container

• Views = Dictionary-level logical join

• JOIN in ABAP = Program-level logical join