输入文件的记录为：8712351,8712353,8712353,8712354,8712356,8712352,87123558712352,8712355
使用COBOL，我需要从上述文件中删除重复项并写入输出文件。我编写了简单的逻辑来读取记录并写入输出文件。
我需要在哪里放置从上述文件中删除重复项（例如8712353、8712352）的逻辑？
这是程序逻辑：
IDENTIFICATION DIVISION.
PROGRAM-ID.RemoveDup.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT INPUTFILEDUP ASSIGN TO 'C:\Cobol\INPUTFILEDUP.txt'
ORGANIZATION IS LINE SEQUENTIAL.
SELECT OUTFILEDUP ASSIGN TO 'C:\Cobol\OUTFILEDUP.txt'
ORGANIZATION IS LINE SEQUENTIAL.
DATA DIVISION.
FILE SECTION.
FD INPUTFILEDUP.
01 INPUTFILEDUPREC.
88 EOFINPUTFILEDUP VALUE HIGH-VALUES.
02 INPUTFILEID PIC 9(07).
FD OUTFILEDUP.
01 OUTFILEDUPREC PIC 9(07).
WORKING-STORAGE SECTION.
77 WS-VARIABLE PIC 9(09).
77 REC-NOT-MATCH PIC 9(01).
77 CUR-VARIABLE PIC 9(09).
PROCEDURE DIVISION.
BEGIN.
OPEN INPUT INPUTFILEDUP
OPEN OUTPUT OUTFILEDUP
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
END-READ
PERFORM UNTIL (EOFINPUTFILEDUP)
WRITE OUTFILEDUPREC FROM INPUTFILEID
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
PERFORM UNTIL (EOFINPUTFILEDUP)
END-READ
END-PERFORM
CLOSE INPUTFILEDUP
CLOSE OUTFILEDUP
STOP RUN.
我将tnput文件按升序排序为：
8712351,8712353,8712353,8712354,8712356,8712352,8712355,8712352,8712355
并且它起作用了，下面是修改后的代码：
但是如果我的文件不是升序还是降序，那么在删除重复项之前我需要在其中编写排序逻辑。如何更新下面的代码呢？正如我尝试过的，但是如果输入文件的结构像这样，则我这样做没有成功：
8712351,8712353,8712353,8712354,8712356,8712352,8712355,8712352,8712355
IDENTIFICATION DIVISION.
PROGRAM-ID.RemoveDup2.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT INPUTFILEDUP ASSIGN TO 'C:\Cobol\INPUTFILEDUP.txt'
ORGANIZATION IS LINE SEQUENTIAL.
SELECT OUTFILEDUP ASSIGN TO 'C:\Cobol\OUTFILEDUP.txt'
ORGANIZATION IS LINE SEQUENTIAL.
DATA DIVISION.
FILE SECTION.
FD INPUTFILEDUP.
01 INPUTFILEDUPREC.
88 EOFINPUTFILEDUP VALUE HIGH-VALUES.
02 INPUTFILEID PIC 9(07).
FD OUTFILEDUP.
01 OUTFILEDUPREC PIC 9(07).
WORKING-STORAGE SECTION.
77 WS-VARIABLE PIC 9(09) VALUE ZERO.
77 REC-NOT-MATCH PIC 9(01).
77 CUR-VARIABLE PIC 9(7) VALUE ZERO.
PROCEDURE DIVISION.
BEGIN.
OPEN INPUT INPUTFILEDUP
OPEN OUTPUT OUTFILEDUP
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
END-READ
PERFORM UNTIL (EOFINPUTFILEDUP)
IF INPUTFILEID NOT EQUAL TO WS-VARIABLE
MOVE INPUTFILEID TO WS-VARIABLE
WRITE OUTFILEDUPREC FROM INPUTFILEID
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
PERFORM UNTIL (EOFINPUTFILEDUP)
ELSE
DISPLAY "dUPLICATE FOUND" INPUTFILEID
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
END-READ
END-PERFORM
CLOSE INPUTFILEDUP
CLOSE OUTFILEDUP
STOP RUN.
最后成功了。
这里是代码：
IDENTIFICATION DIVISION.
PROGRAM-ID.RemoveDup2.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT INPUTFILEDUP ASSIGN TO 'C:\Cobol\INPUTFILEDUP.txt'
ORGANIZATION IS LINE SEQUENTIAL.
SELECT OUTFILEDUP ASSIGN TO 'C:\Cobol\OUTFILEDUP.txt'
ORGANIZATION IS LINE SEQUENTIAL.
SELECT WorkFile ASSIGN TO "WORK.TMP".
DATA DIVISION.
FILE SECTION.
FD INPUTFILEDUP.
01 INPUTFILEDUPREC.
88 EOFINPUTFILEDUP VALUE HIGH-VALUES.
02 INPUTFILEID PIC 9(07).
FD OUTFILEDUP.
01 OUTFILEDUPREC PIC 9(07).
SD WorkFile.
01 WORKREC.
02 WINPUTFILEID PIC 9(07).
WORKING-STORAGE SECTION.
77 WS-VARIABLE PIC 9(09) VALUE ZERO.
77 REC-NOT-MATCH PIC 9(01).
77 CUR-VARIABLE PIC 9(7) VALUE ZERO.
PROCEDURE DIVISION.
BEGIN.
SORT WorkFile ON ASCENDING KEY WINPUTFILEID
USING INPUTFILEDUP GIVING INPUTFILEDUP
OPEN INPUT INPUTFILEDUP
OPEN OUTPUT OUTFILEDUP
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
END-READ
PERFORM UNTIL (EOFINPUTFILEDUP)
IF INPUTFILEID NOT EQUAL TO WS-VARIABLE
MOVE INPUTFILEID TO WS-VARIABLE
WRITE OUTFILEDUPREC FROM INPUTFILEID
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
PERFORM UNTIL (EOFINPUTFILEDUP)
ELSE
DISPLAY "DUPLICATE FOUND " INPUTFILEID
READ INPUTFILEDUP
AT END SET EOFINPUTFILEDUP TO TRUE
END-READ
END-PERFORM
CLOSE INPUTFILEDUP
CLOSE OUTFILEDUP
STOP RUN.
[Organization为Sequential时，删除的记录是最后读取的记录。仅当对文件的最后一个操作成功执行Delete语句时，Read语句才有效。如果不是，则Delete返回43的File Status值。由于当文件为Delete Access的File Status时，Open无法返回以2开头的Sequential值，因此在Invalid Key不允许Delete。
当为文件选择Dynamic或Random访问时，与Delete一样，Rewrite陈述的限制也略有减少。删除的记录无需事先读取。只需在文件说明中填写主要的Key信息，然后发出Delete语句。如果记录不存在，则返回File Status为23且存在Invalid Key条件。
从]的第274页>
Sams Teach Yourself COBOL in 24 Hours
第274页（我刚刚从书架上除掉了灰尘）。因此，在您的情况下，您可能会设置要按INPUTFILEID进行排序的记录，在经历给定INPUTFILEID的首次出现之后进行记录，并据此记录Delete（在编写完之后它到您的输出文件）。
如果要在使用cobol程序读取文件之前使用外部排序对文件进行排序，则可以使用SORT关键字EQUALS删除重复项。如果您在cobol程序之前对文件进行排序并且不删除重复项，那么简单的IF语句和保存字段将允许您删除重复项。