In AT FIRST and AT LAST event blocks the numeric values in the work area contains zeros. SUM statement calculates the totals of numeric fields and places the totals in the corresponding fields of work area.
In AT NEW and AT END OF event blocks SUM statement finds all the rows within the control level and calculates the totals of numeric fields that are right to the control level and places the totals in the corresponding fields of work area.
DATA: gwa_spfli TYPE spfli. DATA: gt_spfli TYPE TABLE OF spfli. SELECT * UP TO 5 ROWS FROM spfli INTO TABLE gt_spfli. LOOP AT gt_spfli INTO gwa_spfli. AT FIRST. WRITE:/ 'Flight Details'. WRITE:/ 'Airline Code' COLOR 5,14 'Connection No.' COLOR 5, 29 'Departure City' COLOR 5, 44 'Arival City' COLOR 5, 58 'Distance' COLOR 5. ULINE. ENDAT. AT NEW carrid. WRITE:/ gwa_spfli-carrid, ' : New Airline'. ULINE. ENDAT. WRITE:/14 gwa_spfli-connid,29 gwa_spfli-cityfrom, 44 gwa_spfli-cityto,58 gwa_spfli-distance. AT END OF carrid. ULINE.
WRITE:/ gwa_spfli-carrid,58 gwa_spfli-distance. ULINE. ENDAT. AT LAST.
WRITE:/ 'Total',58 gwa_spfli-distance. WRITE:/ 'End of Loop'. ENDAT. ENDLOOP.
ON CHANGE OF behaves similar to AT NEW. The syntax is as follows.
ON CHANGE OF [or . .]. [ELSE.] ENDON.
DATA: gwa_spfli TYPE spfli. DATA: gt_spfli TYPE TABLE OF spfli. SELECT * UP TO 5 ROWS FROM spfli INTO TABLE gt_spfli. LOOP AT gt_spfli INTO gwa_spfli. AT FIRST. WRITE:/ 'Flight Details'. WRITE:/ 'Airline Code' COLOR 5,14 'Connection No.' COLOR 5, 29 'Departure City' COLOR 5, 44 'Arival City' COLOR 5, 58 'Distance' COLOR 5. ULINE. ENDAT.
ON CHANGE OF gwa_spfli-carrid. WRITE:/ gwa_spfli-carrid, ‘ : New Airline’. ULINE. ENDON.
WRITE:/14 gwa_spfli-connid,29 gwa_spfli-cityfrom, 44 gwa_spfli-cityto,58 gwa_spfli-distance. ENDLOOP.
Below table summarizes the differences between AT NEW and ON CHANGE OF statements.
| AT NEW | ON CHANGE OF |
|---|---|
| It can be used only in AT LOOP statement. | It can be used in any loop like SELECT, DO etc.. |
| Only one control field can be used. | Multiple control fields separated by OR can be used. |
| AT NEW is triggered when a field left to control level changes. | ON CHANGE OF is not triggered when a field left to control level changes. |
| Values in the fields to the right of control level contains asterisks and zeros. | Values in the fields to the right of control level contains original values. |
| ELSE addition cannot be used. | ELSE addition can be used. |
| Changes to work area with AT NEW will be lost. | Changes to work area with ON CHANGE OF will not be lost. |
