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Module 5: Internal Tables & Work Areas

Internal tables are the heart of ABAP programming. Almost every ABAP application uses internal tables to store, process, and manipulate data fetched from the database or received from interfaces.

1. What Are Internal Tables?​

An internal table is a temporary data structure stored in application server memory.

Why Internal Tables Are Important​

  • Store database records
  • Perform calculations and transformations
  • Transfer data between programs
  • Improve performance by minimizing DB access
Key Concept

Internal tables exist only during program runtime and are deleted automatically afterward.

2. Work Areas​

A work area is a single-row structure used to process one record at a time.

Usage​

  • Reading one row from an internal table

  • Modifying a single record

  • Temporary data holder

Traditional Work Area​

DATA: gs_employee TYPE ty_employee.

Inline Work Area​

READ TABLE gt_employee INTO DATA(gs_employee).
Modern ABAP

Prefer inline work areas when scope is limited.

3. Types of Internal Tables​

ABAP provides three main internal table types.

3.1 Standard Tables​

  • Index-based access

  • Allows duplicate entries

  • Slow key-based access

DATA gt_std TYPE STANDARD TABLE OF i.

Use When​

a. Sequential processing

b. Small datasets

c. Order matters

3.2 Sorted Tables​

  • Automatically sorted by key

  • No duplicate keys (by default)

  • Faster read than standard tables

DATA gt_sorted TYPE SORTED TABLE OF i 
WITH UNIQUE KEY table_line.

Use When​

a. Frequent READ operations

b. Sorted data is required

3.3 Hashed Tables​

  • Hash-based access

  • No index

  • Fastest key-based access

  • Unique keys mandatory

DATA gt_hashed TYPE HASHED TABLE OF i
  WITH UNIQUE KEY table_line.

Use When​

a. Large datasets

b. Frequent key-based access

Performance Comparison

Standard < Sorted < Hashed (for key access)

4. Table Keys​

4.1 Primary Key​

  • Defined during table declaration

  • Used for fast access

DATA gt_emp TYPE SORTED TABLE OF ty_employee
  WITH UNIQUE KEY emp_id.

4.2 Secondary Keys (Advanced)​

  • Improve read performance

  • Optional

Best Practice

Define keys consciously. Wrong table type = poor performance.

5. Core Operations on Internal Tables​

5.1 READ TABLE​

Reads a single row from an internal table.

READ TABLE gt_emp INTO DATA(gs_emp)
  WITH KEY emp_id = 1001.

Check result:

IF sy-subrc = 0.
  WRITE 'Record found'.
ENDIF.
Always Check sy-subrc

Ignoring sy-subrc leads to runtime errors.

5.2 LOOP AT​

Iterates over internal table entries.

LOOP AT gt_emp INTO DATA(gs_emp).
  WRITE gs_emp-name.
ENDLOOP.

With condition:

LOOP AT gt_emp INTO DATA(gs_emp)
  WHERE dept = 'IT'.
  WRITE gs_emp-name.
ENDLOOP.

5.3 MODIFY​

Updates existing entries.

MODIFY gt_emp FROM gs_emp.

With key:

MODIFY gt_emp FROM gs_emp
  TRANSPORTING salary
  WHERE emp_id = 1001.

5.4 DELETE​

Deletes rows from internal tables.

DELETE gt_emp WHERE dept = 'HR'.

Delete current loop row:

DELETE gt_emp INDEX sy-tabix.
Caution

Deleting inside loops must be handled carefully to avoid logical errors.

6. Performance Considerations​

6.1 Choose the Right Table Type​

ScenarioRecommended Table
Sequential processingStandard
Sorted accessSorted
Fast key lookupHashed

6.2 Avoid Nested Loops​

❌ Bad Practice

LOOP AT gt_a INTO DATA(ls_a).
  LOOP AT gt_b INTO DATA(ls_b).
    " heavy logic
  ENDLOOP.
ENDLOOP.

✅ Better Approach

  • Use hashed tables

  • Use READ with key

6.3 Avoid Database Access Inside Loops​

❌ Bad Practice

LOOP AT gt_emp INTO DATA(ls_emp).
  SELECT SINGLE * FROM zemp
    WHERE emp_id = ls_emp-emp_id.
ENDLOOP.

✅ Good Practice

SELECT * FROM zemp INTO TABLE @DATA(gt_db).

LOOP AT gt_emp INTO DATA(ls_emp).
  READ TABLE gt_db INTO DATA(ls_db)
    WITH KEY emp_id = ls_emp-emp_id.
ENDLOOP.
Golden Performance Rule

Database access inside loops is one of the biggest performance killers in ABAP.

7. Common Beginner Mistakes​

Avoid These

  • Using STANDARD tables for key-based access

  • Not defining keys

  • Ignoring sy-subrc

  • Unnecessary work areas

  • Nested loops with large datasets

8. Summary​

  • Internal tables are core ABAP data structures

  • Choose the correct table type

  • Define keys properly

  • Use READ, LOOP, MODIFY, DELETE carefully

  • Optimize for performance early

9. Practice Exercises​

  • Create a sorted table with employee data.

  • Read a record using a key.

  • Update salary using MODIFY.

  • Delete records based on condition.

  • Compare performance of STANDARD vs HASHED table.

10. What’s Next?​

➡️ Module 6: Open SQL Basics

Learning Tip

If you master internal tables, performance tuning becomes intuitive.