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.

combine rows from two or more tables based on a related column, usually a key field. ABAP supports various join types (INNER JOIN, LEFT OUTER JOIN, etc.) mostly used inside Open SQL queries.

How to Use Joins:

SELECT a~vbeln, a~erdat, b~posnr, b~matnr
  FROM vbak AS a
  INNER JOIN vbap AS b ON a~vbeln = b~vbeln
  INTO TABLE @DATA(result).

• Here, sales order header (vbak) is joined with sales order items (vbap) on the sales order number (vbeln).
• Result is fetched in one go, improving performance by reducing database calls.

FOR ALL ENTRIES

is a clause in ABAP that allows you to select records from a table where a field matches any entry in an internal table, acting like an “IN” condition.

How to Use FOR ALL ENTRIES:

DATA: lt_vbak TYPE TABLE OF vbak,
      lt_vbap TYPE TABLE OF vbap.

” First select sales orders into internal table
SELECT vbeln erdat vkorg kunnr FROM vbak
  INTO TABLE lt_vbak
  WHERE vkorg = ‘1000’.

” Use FOR ALL ENTRIES to select matching items
IF lt_vbak IS NOT INITIAL.
  SELECT vbeln posnr matnr FROM vbap
    INTO TABLE lt_vbap
    FOR ALL ENTRIES IN lt_vbak
    WHERE vbeln = lt_vbak-vbeln.
ENDIF.

• The first SELECT fetches sales orders for a sales org.
• The second SELECT fetches all items related to these orders.
• This reduces database hits compared to looping with multiple selects.