SY-INDEX
In a loop, a statement block is executed several times in succession. There are four kinds of loops in ABAP:
Unconditional loops using the DO statement.
Conditional loops using the WHILE statement.
Loops through internal tables and extract datasets using the LOOP statement.
Loops through datasets from database tables using the SELECT statement.
This section deals with DO and WHILE loops. SELECT is an Open SQL statement, and is described in the Open SQL section. The LOOP statement is described in the sections on internal tables and extract datasets.
Unconditional Loops
To process a statement block several times unconditionally, use the following control structure:
DO [<n> TIMES] [VARYING <f> FROM <f1> NEXT <f 2>].
<Statement block>
ENDDO.
If you do not specify any additions, the statement block is repeated until it reaches a termination statement such as EXIT or STOP (see below). The system field SY-INDEX contains the number of loop passes, including the current loop pass.
SY-TABIX
You can use the LOOP statement to process special loops for any internal table.
LOOP AT <itab> <result> <condition>.
<statement block>
ENDLOOP.
This reads the lines of the table one by one as specified in the <result> part of the LOOP statement. You can then process them in the statements within the LOOP... ENDLOOP control structure. You can either run the loop for all entries in the internal table, or restrict the number of lines read by specifying a <condition>. Control level processing is allowed within the loop.
The sequence in which the lines are processed depends on the table type:
Standard tables and sorted tables
The lines are processed according to the linear index. Within the processing block, the system field SY-TABIX contains the index of the current line.
Hashed tables
As long as the table has not been sorted, the lines are processed in the order in which you added them to the table. Within the processing block, the system field SY-TABIX is always 0.
Bluesky
