ABAP Using a Cursor to Read Data

雨点打透心脏的1/2处 2022-09-30 03:56 13阅读 0赞

BC - ABAP Programming中三个例子，很好，摘抄如下，以供学习

DATA: C1 TYPE CURSOR,  
C2 TYPE CURSOR.  
DATA: WA1 TYPE SPFLI,  
WA2 TYPE SPFLI.  
DATA: FLAG1,  
FLAG2.  
OPEN CURSOR: C1 FOR SELECT CARRID CONNID  
FROM SPFLI  
WHERE CARRID = 'LH',  
C2 FOR SELECT CARRID CONNID CITYFROM CITYTO  
FROM SPFLI  
WHERE CARRID = 'AZ'.  
DO.  
IF FLAG1 NE 'X'.  
FETCH NEXT CURSOR C1 INTO CORRESPONDING FIELDS OF WA1.  
IF SY-SUBRC <> 0.  
CLOSE CURSOR C1.  
FLAG1 = 'X'.  
ELSE.  
WRITE: / WA1-CARRID, WA1-CONNID.  
ENDIF.  
ENDIF.  
IF FLAG2 NE 'X'.  
FETCH NEXT CURSOR C2 INTO CORRESPONDING FIELDS OF WA2.  
IF SY-SUBRC <> 0.  
CLOSE CURSOR C2.  
FLAG2 = 'X'.  
ELSE.  
WRITE: / WA2-CARRID, WA2-CONNID,  
WA2-CITYFROM, WA2-CITYTO.  
ENDIF.  
ENDIF.  
IF FLAG1 = 'X' AND FLAG2 = 'X'.  
EXIT.  
ENDIF.  
ENDDO.

DATA C TYPE CURSOR.  
DATA WA TYPE SBOOK.  
OPEN CURSOR C FOR SELECT CARRID CONNID FLDATE BOOKID SMOKER  
FROM SBOOK  
ORDER BY CARRID CONNID FLDATE SMOKER BOOKID.  
FETCH NEXT CURSOR C INTO CORRESPONDING FIELDS OF WA.  
WHILE SY-SUBRC = 0.  
IF WA-SMOKER = ' '.  
PERFORM NONSMOKER USING C.  
ELSEIF WA-SMOKER = 'X'.  
PERFORM SMOKER USING C.  
SKIP.  
ELSE.  
EXIT.  
ENDIF.  
ENDWHILE.  
FORM NONSMOKER USING N\_CUR TYPE CURSOR.  
WHILE WA-SMOKER = ' ' AND SY-SUBRC = 0.  
FORMAT COLOR = 5.  
WRITE: / WA-CARRID, WA-CONNID, WA-FLDATE, WA-BOOKID.  
FETCH NEXT CURSOR N\_CUR INTO CORRESPONDING FIELDS OF WA.  
ENDWHILE.  
ENDFORM.  
FORM SMOKER USING S\_CUR TYPE CURSOR.  
WHILE WA-SMOKER = 'X' AND SY-SUBRC = 0.  
FORMAT COLOR = 6.  
WRITE: / WA-CARRID, WA-CONNID, WA-FLDATE, WA-BOOKID.  
FETCH NEXT CURSOR S\_CUR INTO CORRESPONDING FIELDS OF WA.  
ENDWHILE.  
ENDFORM.

The program opens a cursor for the database table SBOOK. After the first FETCH  
statement, a subroutine is called, which is dependent on the contents of the  
SMOKER column. The cursor is passed to an interface parameter in the subroutine.  
The subroutines read further lines until the contents of the SMOKER column change.  
The subroutines perform different tasks using the lines read by the cursor.

DATA: WA\_SPFLI TYPE SPFLI,  
WA\_SFLIGHT TYPE SFLIGHT.  
DATA: C1 TYPE CURSOR,  
C2 TYPE CURSOR.  
OPEN CURSOR C1 FOR SELECT \*  
FROM SPFLI  
ORDER BY PRIMARY KEY.

OPEN CURSOR C2 FOR SELECT \*  
FROM SFLIGHT  
ORDER BY PRIMARY KEY.  
DO.  
FETCH NEXT CURSOR C1 INTO WA\_SPFLI.  
IF SY-SUBRC NE 0.  
EXIT.  
ENDIF.  
WRITE: / WA\_SPFLI-CARRID, WA\_SPFLI-CONNID.  
DO.  
FETCH NEXT CURSOR C2 INTO WA\_SFLIGHT.  
IF SY-SUBRC <> 0 OR WA\_SFLIGHT-CARRID <> WA\_SPFLI-CARRID  
OR WA\_SFLIGHT-CONNID <> WA\_SPFLI-CONNID.  
EXIT.  
ELSE.  
WRITE: / WA\_SFLIGHT-CARRID, WA\_SFLIGHT-CONNID,  
WA\_SFLIGHT-FLDATE.  
ENDIF.  
ENDDO.

The program opens a cursor for each of the table SPFLI and SFLIGHT. Since both  
tables are linked by a foreign key relationship, it is possible to program a nested loop  
by sorting the selection by its primary key, so that the data read in the inner loop  
depends on the data in the outer loop. This programming method is quicker than  
using nested SELECT statements, since the cursor for the inner loop does not  
continually have to be reopened.