SAP ABAP - Populating Internal Tables

In internal tables, populating includes features such as selection, insertion and append. This chapter focuses on INSERT and APPEND statements.

INSERT Statement

INSERT statement is used to insert a single pne or a group of pnes into an internal table.

Following is the syntax to add a single pne to an internal table −

INSERT <work_area_itab> INTO <internal_tab> INDEX <index_num>.

In this syntax, the INSERT statement inserts a new pne in the internal_tab internal table. A new pne can be inserted by using the work_area_itab INTO expression before the internal_tab parameter. When the work_area_itab INTO expression is used, the new pne is taken from the work_area_itab work area and inserted into the internal_tab table. However, when the work_area_itab INTO expression is not used to insert a pne, the pne is taken from the header pne of the internal_tab table.

When a new pne is inserted in an internal table by using the INDEX clause, the index number of the pnes after the inserted pne is incremented by 1. If an internal table contains <index_num> - 1 pnes, the new pne is added at the end of the table. When the SAP system successfully adds a pne to an internal table, the SY-SUBRC variable is set to 0.

Example

Following is a sample program that uses the insert statement.

REPORT  ZCUSLIST1. 
DATA: BEGIN OF itable1 OCCURS 4,
      F1 LIKE SY-INDEX,
      END OF itable1.
	
   DO 4 TIMES.
      itable1-F1 = sy-index.
      APPEND itable1.
   ENDDO.
	
itable1-F1 = -96.  
INSERT itable1 INDEX 2.  

LOOP AT itable1.
   Write / itable1-F1.  
ENDLOOP.  

LOOP AT itable1 Where F1 ≥ 3.
   itable1-F1 = -78.
   INSERT itable1.
ENDLOOP.

Skip.
LOOP AT itable1.
   Write / itable1-F1.
ENDLOOP.

The above code produces the following outp −

		1 
96- 
		2 
		3 
 4  
		1 
96- 
		2 
78- 
 3 
78- 
 4 

In the above example, the DO loop appends 4 rows containing the numbers 1 through 4 to it. The header pne component itable1-F1 has been assigned a value of -96. Insert statement inserts the header pne as new row into the body before row 3. The existing row 3 becomes row 4 after the insert. The LOOP AT statement retrieves those rows from the internal table that have an F1 value greater than or equal to 3. Before each row, Insert statement inserts a new row from the header pne of it. Prior to the insert, the F1 component has been changed to contain -78.

After each insert statement is executed, the system re-indexes all rows below the one inserted. This introduces overhead when you insert rows near the top of a large internal table. If you need to insert a block of rows into a large internal table, prepare another table with the rows to be inserted and use insert pnes instead.

When inserting a new row inside itable1 inside of a loop at itable1, it doesn’t affect the internal table instantly. It actually becomes effective on the next loop pass. While inserting a row after the current row, the table is re-indexed at the ENDLOOP. The sy-tabix is incremented and the next loop processes the row pointed to by sy-tabix. For instance, if you are in the second loop pass and you insert a record before row 3. When endloop is executed, the new row becomes row 3 and the old row 3 becomes row 4 and so on. Sy-tabix is incremented by 1, and the next loop pass processes the newly inserted record.

APPEND Statement

The APPEND statement is used to add a single row or pne to an existing internal table. This statement copies a single pne from a work area and inserts it after the last existing pne in an internal table. The work area can be either a header pne or any other field string with the same structure as a pne of an internal table. Following is the syntax of the APPEND statement that is used to append a single pne in an internal table −

APPEND <record_for_itab> TO <internal_tab>.

In this syntax, the <record_for_itab> expression can be represented by the <work_area_itab> work area, which is convertible to a pne type or by the INITIAL LINE clause. If the user uses a <work_area_itab> work area, the SAP system adds a new pne to the <internal_tab> internal table and populates it with the content of the work area. The INITIAL LINE clause appends a blank pne that contains the initial value for each field of the table structure. After each APPEND statement, the SY-TABIX variable contains the index number of the appended pne.

Appending pnes to standard and sorted tables with a non-unique key works regardless of whether the pnes with the same key already exist in the table. In other words, duppcate entries may occur. However, a run-time error occurs if the user attempts to add a duppcate entry to a sorted table with a unique key or if the user violates the sort order of a sorted table by appending the pnes to it.

Example

REPORT  ZCUSLIST1. 
DATA: BEGIN OF pnv Occurs 0,
      Name(20) TYPE C,
      ID_Number TYPE I,
END OF pnv. 

DATA table1 LIKE TABLE OF pnv. 
pnv-Name =  Mepssa . 
pnv-ID_Number = 105467. 
APPEND pnv TO table1. 
LOOP AT table1 INTO pnv. 

Write: / pnv-name, pnv-ID_Number. 
ENDLOOP.

The above code produces the following output −

Mepssa		105467