Control Structures

Conditionals and loops, the CHECK statement and its context-dependent behaviour, and the system fields that go with them.

ABAP control flow resembles other languages, with a few statements of its own — CHECK and EXIT in particular — whose behaviour is worth knowing precisely.

IF

Conditionals

IF lv_amount > 10000.
  lv_discount = 10.
ELSEIF lv_amount > 5000.
  lv_discount = 5.
ELSE.
  lv_discount = 0.
ENDIF.

IF lv_matnr IS INITIAL.
  " not set
ENDIF.

IF lt_items IS NOT INITIAL.
  " has rows
ENDIF.

Comparison operators

Operator	Alternative	Meaning
=	EQ	Equal
<>	NE	Not equal
<	LT	Less than
>	GT	Greater than
BETWEEN a AND b	—	Within a range
IS INITIAL	—	Equal to the type initial value
IN	—	Matches a ranges table
CS	—	Contains string
CP	—	Contains pattern

CASE

Branching on one value

CASE lv_status.
  WHEN 'A'.       lv_text = 'Received'.
  WHEN 'B' OR 'C'. lv_text = 'In progress'.
  WHEN 'Z'.       lv_text = 'Complete'.
  WHEN OTHERS.    lv_text = 'Unknown'.
ENDCASE.

DO and WHILE

Counted and conditional loops

DO 10 TIMES.
  WRITE: / sy-index.
ENDDO.

DO.
  IF lv_count > 100. EXIT. ENDIF.
  lv_count = lv_count + 1.
ENDDO.

WHILE lv_flag = abap_true.
  " ...
ENDWHILE.

LOOP over internal tables

Looping

LOOP AT lt_items INTO DATA(ls_item).
  WRITE: / ls_item-matnr.
ENDLOOP.

LOOP AT lt_items ASSIGNING FIELD-SYMBOL(<fs_item>).
  <fs_item>-menge = <fs_item>-menge * 2.
ENDLOOP.

LOOP AT lt_items INTO ls_item WHERE menge > 100.
ENDLOOP.

Loop control

Statement	Behaviour
EXIT	Leave the loop entirely
CONTINUE	Skip to the next iteration
CHECK cond	If the condition is false, behave like CONTINUE

System fields

Field	Content
sy-subrc	Return code of the preceding statement; 0 means success
sy-index	Iteration counter in DO and WHILE
sy-tabix	Row index in LOOP
sy-datum / sy-uzeit	Current date and time
sy-uname	Logged-on user
sy-mandt	Client
sy-langu	Logon language

IF