Preface – This post is part of the ABAP Beginner series.
Very often, there is a situation in ABAP where we need to store multiple data of a definite structure at runtime and perform some operations upon them. For runtime operations we cannot hit database every time. In that situation, we fetch required data from database table, store it in something called ABAP Internal Table and perform operations upon them.
Table of Contents
Definition
An Internal table in ABAP is a runtime copy of a table or structure. It is a reusable object. Each line of an internal table has same structure. In SAP, Internal table is an alternative to Arrays.
ABAP Internal Table – Illustration Image
Syntax
DATA: <YOUR_INTERNAL_TABLE_NAME> TYPE TABLE OF <Structure, Table, Data type, Table Type>.
Note: An Internal table can also be defined at runtime. It is explained in one of the example below.
Examples
Case 1:
DATA: itab_emp TYPE TABLE OF zemployee. // Declaration of Internal table SELECT * FROM zemployee INTO TABLE itab_emp. // feeding data in internal table
Case 2:
SELECT * FROM zemployee INTO TABLE @DATA (itab_emp). // Declaration of Internal table at runtime and feeding data there itself
Types of ABAP Internal Tables
According to the frequency of use, internal tables are of following types:
| Type | Description | Example |
| Standard tables | A standard Internal table is the one which is accessed by its index. In this table we APPEND data one by one and later access data (Read, Modify and Delete) using INDEX statement. | DATA: itab_emp TYPE TABLE OF zemployee. |
| Sorted tables | A sorted internal table is just like a standard internal table except data is inserted not appended. It is sorted as we fill it. We fill sorted table using INSERT statement. | DATA: itab_emp TYPE SORTED TABLE OF zemployee WITH UNIQUE KEY empid. |
| Hashed tables | A hashed internal table is the one in which data is filled using UNIQUE KEY. To access data we need this key. | DATA: itab_emp TYPE HASHED TABLE OF zemployee WITH UNIQUE KEY empid empname. |
Operations on ABAP Internal Tables
Operations on Entire Internal Tables | |
| Assigning Internal Tables | MOVE itab1 TO itab2. OR itab2 = itab1. |
| Initialize Internal Tables | CLEAR itab => To clear the header of the table CLEAR itab [] => To initialize the table but the initial memory remains reserved. REFRESH itab => Clears data of table but the initial memory remains reserved. It is same as CLEAR itab []. FREE itab =>It clears data as well as the initial memory allocated to the table. |
| Compare Internal Tables | Suppose we have two Internal tables ITAB1 and ITAB2 with same data type but different number of data, let us say 2 and 3 Lines of data respectively. The statement returns Boolean result. ITAB1 GT ITAB2 (Greater than) => False
ITAB1 EQ ITAB2 (Equal to) => False
ITAB1 LE ITAB2 ( Less than or equal to) => True
ITAB1 NE ITAB2 (Not Equal to) => True
ITAB1 LT ITAB2 (Less than) => True |
| Sort Internal Tables | SORT itab [ASCENDING|DESCENDING] [AS text] [STABLE]. The default is ascending order. |
| Internal Tables as Interface Parameters | We can use Internal table as a parameter in Forms and Interfaces. In forms Internal Table is written in addition to USING and CHANGING. |
| Determining the Attributes of Internal Tables | DESCRIBE TABLE itab [LINES lv_lin] [OCCURS lv_n] [KIND lv_knd]. If you use LINES, it gives number of rows in Internal table. If you use OCCURS, it gives initial size of Internal table. If you use KIND, it gives type of Internal table. |
Operations on Individual Lines | |
| Access Methods for Individual Table Entries | 1. Using Work Area READ TABLE <itable> [INTO <wa>] INDEX <idx>. 2. Field Symbol READ TABLE <itable> ASSINGING FIELD SYMBOL(<fs_tab>) |
| Filling Internal Tables Line by Line | APPEND [<wa> TO / INITIAL LINE TO] <itab>. |
| Reading Table Lines | READ TABLE itab FROM wa result.
or using a key
READ TABLE itab WITH TABLE KEY k1 = f1 … kn = fn result.
Both the above statements set sy-subrc value to 0 & 4 for success and failure search cases respectively. |
| Processing Table Lines in Loops | LOOP AT itab result condition. statement block ENDLOOP. The result part can be work area or field symbol. |
| Changing Table Lines | MODIFY TABLE itab FROM wa [TRANSPORTING f1 f2 …] [WHERE condition]. The given statement modifies single record based on condition. In Transporting we can give specific column/field we want to modify. |
| Deleting Table Lines | DELETE TABLE itab FROM wa.
or using a key
DELETE TABLE itab WITH TABLE KEY k1 = f1 … kn = fn. |
| Searching Through Internal Tables Line by Line | 1. FIND IN TABLE FIND [{FIRST OCCURRENCE}|{ALL OCCURRENCES} OF] pattern IN TABLE itab [IN {BYTE|CHARACTER} MODE] · [{FIRST OCCURRENCE}|{ALL OCCURRENCES} tells if search is only for first findings or for all · “pattern” is the string being searched for · [IN {BYTE|CHARACTER} MODE] tells if the search will be character wise or byte wise
2. REPLACE IN TABLE REPLACE [{FIRST OCCURRENCE}|{ALL OCCURRENCES} OF] pattern IN TABLE itab … WITH new [IN {BYTE|CHARACTER} MODE] · The way FIND works in same way, it also finds and replaces the pattern with new |
*** We will discuss all these operations in a separate post for better clarification.
Open SQL in ABAP Internal Table
The way we access and manipulate data in tables of SAP ABAP, in the same way we can use open SQL to manipulate data of internal tables
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