ABAP – Nested Loops

             The DO and WHILE statements can be tested as well as combined with other loop forms. Each nested loop will have it’s own SY-INDEX created and monitored by the system.

Syntax:-

The syntax for nested DO loop is:

DO [n TIMES].
<statement block n>.
DO [m TIMES].
<statement block m>.
ENDDO.
ENDDO.

Example:-

REPORT YS_SEP_15.
Data: a1 type I, b1 type I.
a1 = 0.
b1 = 0.
Do 2 times.
a1 = a1 + 1.
Write: /'Outer', a1.
Do 10 times.
b1 = b1 + 1.
Write: /'Inner', b1.
ENDDo.
ENDDo.

The above code produces the following output:

Outer 1
Inner 1
Inner 2
Inner 3
Inner 4
Inner 5
Inner 6
Inner 7
Inner 8
Inner 9
Inner 10
Outer 2
Inner 11
Inner 12
Inner 13
Inner 14
Inner 15
Inner 16
Inner 17
Inner 18
Inner 19
Inner 20

    In this example, the outer DO loop is processed twice and the inner DO loop is processed 10 times, each time the outer DO loop is processed. So in this case, the inner loop is processed 20 times.