I need a simple and practical explanation of how to display data from an internal table in an ALV grid. I also want to understand how to improve the report by adding useful features such as column headings, sorting, filtering, totals, and layout options.

Please help with the following points:

• What is CL_SALV_TABLE and when should it be used instead of REUSE_ALV_GRID_DISPLAY or CL_GUI_ALV_GRID?
• How can we create a basic ALV report using an internal table?
• How can we define column texts and hide unwanted columns?
• How can we enable sorting, filtering, and standard toolbar functions?
• How can we add totals and subtotals for numeric fields?
• How can we set zebra pattern, optimize column width, and change the ALV title?
• How can we handle exceptions while creating an ALV object?
• How can we add a hotspot or clickable column in CL_SALV_TABLE?
• What are the limitations of CL_SALV_TABLE, especially for editable ALV reports?
• Can someone share a complete working ABAP example with sample data?

A beginner-friendly, step-by-step guide with complete ABAP code and explanation would be very helpful.

The current program contains multiple SELECT statements inside loops, nested loops, and repeated reads on standard internal tables. It works for small data volumes, but performance becomes very slow in production.

I would like to understand the best practices for improving ABAP performance when working with large internal tables.

Please help with the following points:

• When should we use standard, sorted, and hashed internal tables?
• What is the difference between READ TABLE, table expressions, and binary search from a performance perspective?
• How can we avoid SELECT statements inside loops?
• When should FOR ALL ENTRIES be used, and what checks are required before using it?
• How can joins, CDS views, and Open SQL reduce database calls?
• When is it better to use LOOP AT ... GROUP BY, REDUCE, FILTER, or FOR expressions?
• How can nested loops be replaced with efficient internal table processing?
• Which tools can be used to identify ABAP performance bottlenecks, such as SAT, ST05, SQL Monitor, and ATC?
• What are common ABAP performance mistakes that should be avoided in real projects?
• Can someone share a before-and-after ABAP code example for performance optimization?

A practical explanation with examples, performance comparison, and recommended coding standards would be very helpful.

DATA: lo_descr TYPE REF TO cl_abap_structdescr,
lo_table TYPE REF TO cl_abap_tabledescr,
lr_data TYPE REF TO data,
lr_line TYPE REF TO data.

“— Step 1: Define a structure dynamically
lo_descr = cl_abap_structdescr=>create(
VALUE #( ( name = ‘FIELD1’ type = cl_abap_elemdescr=>get_c( 10 ) )
( name = ‘FIELD2’ type = cl_abap_elemdescr=>get_i( ) ) )
).

“— Step 2: Create internal table description
lo_table = cl_abap_tabledescr=>create( lo_descr ).

“— Step 3: Create actual data object (the table)
CREATE DATA lr_data TYPE HANDLE lo_table.
ASSIGN lr_data->* TO FIELD-SYMBOL(<itab>).

“— Step 4: Create a line type and assign
CREATE DATA lr_line TYPE HANDLE lo_descr.
ASSIGN lr_line->* TO FIELD-SYMBOL(<wa>).

“— Step 5: Fill dynamically created table
<wa>-field1 = ‘Hello’.
<wa>-field2 = 123.
APPEND <wa> TO <itab>.

<wa>-field1 = ‘World’.
<wa>-field2 = 456.
APPEND <wa> TO <itab>.

“— Step 6: Loop through the dynamic internal table
LOOP AT <itab> ASSIGNING <wa>.
WRITE: / <wa>-field1, <wa>-field2.
ENDLOOP.

Key Points:

1. Use RTTS (Runtime Type Services) → cl_abap_structdescr, cl_abap_tabledescr, cl_abap_elemdescr.
2. Create data objects at runtime with CREATE DATA ... TYPE HANDLE.
3. Use field symbols (<itab>, <wa>) to access the data.

*&---------------------------------------------------------------------*
*& Report  ZTEST_PROGRAM_2
*&
*&---------------------------------------------------------------------*
*&
*&
*&---------------------------------------------------------------------*

REPORT ztest_program_2.

TYPES : BEGIN OF lty_student,
        name TYPE string,
        id TYPE zstudent_id_01,
        departid TYPE zdep_id,
        departmentname TYPE string,
        END OF lty_student.


" internal table
DATA lt_student TYPE TABLE OF lty_student.

" work area.
DATA ls_student TYPE lty_student.
DATA ls_department TYPE zdepartment_1.

" assign  -->
" unassig  --> directly access the place where the data is stored.


START-OF-SELECTION.

  SELECT studentname studentid departmentid FROM zstudent_2
        INTO TABLE lt_student.

  "using workarea.
  clear: ls_Student.
  ls_student-id = '2'.
  ls_student-name = 'RAM'.
  ls_student-departid = '4'.
  ls_student-departmentname = 'CSE'.

  " append
   append ls_Student to lt_Student.

    "using workarea.
  clear: ls_Student.
  ls_student-id = '3'.
  ls_student-name = 'RAM'.
  ls_student-departid = '5'.
  ls_student-departmentname = 'CSE'.

  " append
   insert ls_Student into lt_Student.



  LOOP AT lt_student INTO ls_student.
    WRITE: / ls_student-name, ls_student-id, ls_student-departid, ls_Student-departmentname.
  ENDLOOP. 

  This ABAP report ZTEST_PROGRAM_2 is a beginner-friendly example that demonstrates how to work with internal tables, work areas, and database records. It starts by defining a custom structure lty_student to hold student details such as ID, name, department ID, and department name. An internal table lt_student and a work area ls_student are then declared to store and process this data. The program first fetches existing records from the custom database table zstudent_2 into the internal table using a SELECT ... INTO TABLE statement. After that, new student entries are created manually by filling values into the work area and adding them to the internal table using both APPEND and INSERT. Finally, the program loops through the internal table and displays each student’s details on the output screen. Overall, the code provides a simple but practical illustration of how internal tables can combine database data with additional records and then be processed for reporting in ABAP.