HP 3000 Manuals

SORT-MERGE/XL Programmer's Guide

Keys 

When information is sorted or merged, keys determine the output record
sequence.  Keys are defined by their beginning position, length, key
type, and ordering sequence (ascending or descending).

For example, to sort by last names with the record format below, you
would specify a key that begins in column 1 and is 20 characters long,
byte (ASCII) type, and ascending sequence.

     Last Name            First Name          Employee Number     Hire Date

     Jackson,             Jonathan            000006              06/06/87

     0         1         2         3         4         5         6
     123456789012345678901234567890123456789012345678901234567890123456789

You can specify the collating sequence, which is the order by which the
keys are sorted.  You can use a predefined order, like ASCII, EBCDIC, or
a Native Language, or you can define your own collating sequence.

You may use multiple keys.  The major key determines the part of the
record examined first in the sort.  As Figure 1-4 shows if the major keys
of two records are the same, the secondary keys determine the new
sequence of the records.  If two records have the same first keys and the
same second keys, their third keys are compared to determine the
sequence.  If all the key fields in two or more records are identical,
the output file preserves the order of the input records.


          Figure 1-4.  Key Comparing Operations 

For more information about specifying keys, refer to Chapter 2.  For more
information about collating sequences, refer to Chapter 4.

MPE/iX 5.0 Documentation