SORT and MERGE
If you wished to take a file of unordered records and
produce a new file of these records sorted into ascending or descending order of
a field you would use SORT.
A D V E R T I S E M E N T
The
League table program in the
Sample code section uses this utility to generate a league table from updated
records from a data file, sorted principally by descending points.
Consider this segment of code from this program:
000050 ENVIRONMENT DIVISION.
000060 INPUT-OUTPUT SECTION.
000070 FILE-CONTROL.
000080 SELECT TEAM-REC-IN ASSIGN TO "INPUT.REC"
000090 ORGANIZATION IS SEQUENTIAL.
000100 SELECT WORK-FILE ASSIGN TO SORTWK01.
000110 SELECT SORT-OUT ASSIGN TO "SORTED.REC"
000120 ORGANIZATION IS SEQUENTIAL.
000130 SELECT PRINT-FILE ASSIGN TO "PRINTOUT.TXT".
000140
000150
000160 DATA DIVISION.
000170 FILE SECTION.
000180 FD TEAM-REC-IN.
000190 01 TEAM-REC.
000200 03 TEAM-CODE PIC XXX.
000210 03 TEAM-NAME PIC X(20).
000220 03 PLAYED PIC 99.
000230 03 GOALS-FOR PIC 99.
000240 03 GOALS-AGST PIC 99.
000250 03 G-WON PIC 99.
000260 03 G-LOST PIC 99.
000270 03 G-DRAWN PIC 99.
000280 03 GOAL-DIFF PIC S99 SIGN LEADING SEPARATE.
000290 03 POINTS PIC 99.
000300
000310 SD WORK-FILE.
000320 01 WORK-REC.
000330 03 TEAM-CODE-KEY PIC XXX.
000340 03 PIC X(22).
000350 03 GF-KEY PIC 99.
000360 03 PIC X(8).
000370 03 GD-KEY PIC S99 SIGN LEADING SEPARATE.
000380 03 POINTS-KEY PIC 99.
000390
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In addition to the FD for the TEAM-REC-IN
(the main data file) there is also a WORK-FILE that the computer uses for
sorting. Here it is assigned to SORTWK01, required for the Fujitsu COBOL
compiler, but for MicroFocus you might code ASSIGN TO DISK or even ASSIGN TO "B:TEMPFILE".
The WORK-FILE does not have a FD descriptor, but rather,
has a sort descriptor SD.
003310 SORT-TABLE.
003320 SORT WORK-FILE
003330 ON DESCENDING KEY POINTS-KEY GD-KEY GF-KEY
003340 USING TEAM-REC-IN
003350 GIVING SORT-OUT.
The SORT-TABLE paragraph then sorts the data
file TEAM-REC-IN as shown above. Note that the SORT verb is followed by
WORK-FILE and that TEAM-REC-IN is refered to with USING...
Since it is common for two teams to have the same number
of points then, the DESCENDING KEY first attempts to sort by points (POINTS-KEY)
but if these match then they are than sorted by goal difference (GD-KEY) and
then by goals scored (GF-KEY). If these all match then the teams will be placed
as the appear from the data file (for TEAM-REC-IN I placed them in alphabetical
order).
SORT-OUT is the destination of the sorted data where the
new league table would appear. Note, a file that is to be sorted if already open, must be
closed prior to sorting. THE SORT STATEMENT WILL AUTOMATICALLY OPEN THE UNSORTED
FILE WHEN EXECUTED. Merge To merge two sorted files into a single sorted file, the
MERGE statement is used:
MERGE WORK-FILE
ON ASCENDING KEY CUS-CODE-KEY
USING FILE-A
FILE-B
GIVING MERGED-FILE
You can merge more than 2 files if you wish. An SD would
be required as used with a SORT
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