Keyed fields defined as character fields can be arranged based
either on the sequence for EBCDIC characters or on an alternative collating
sequence.
Consider the following records.
| Record |
Empname |
Deptnbr |
Empnbr |
|---|
| 1 |
Jones, Mary |
45 |
23318 |
| 2 |
Smith, Ron |
45 |
41321 |
| 3 |
JOHNSON, JOHN |
53 |
41322 |
| 4 |
Smith, ROBERT |
27 |
56218 |
| 5 |
JONES, MARTIN |
53 |
62213 |
|
If the Empname is the key field and is a character field, using
the sequence for EBCDIC characters, the records can be arranged as follows.
| Record |
Empname |
Deptnbr |
Empnbr |
|---|
| 1 |
Jones, Mary |
45 |
23318 |
| 3 |
JOHNSON, JOHN |
53 |
41322 |
| 5 |
JONES, MARTIN |
53 |
62213 |
| 2 |
Smith, Ron |
45 |
41321 |
| 4 |
Smith, ROBERT |
27 |
56218 |
|
Notice that the EBCDIC sequence causes an unexpected sort order because
the lowercase characters are sorted before uppercase characters. Thus, Smith,
Ron sorts before Smith, ROBERT. An alternative collating
sequence can be used to sort the records when the records were entered using
uppercase and lowercase as shown in the following example.
| Record |
Empname |
Deptnbr |
Empnbr |
|---|
| 3 |
JOHNSON, JOHN |
53 |
41322 |
| 5 |
JONES, MARTIN |
53 |
62213 |
| 1 |
Jones, Mary |
45 |
23318 |
| 4 |
Smith, ROBERT |
27 |
56218 |
| 2 |
Smith, Ron |
45 |
41321 |
|
To use an alternative collating sequence for a character key field, specify
the ALTSEQ DDS keyword, and specify the name of the table containing the alternative
collating sequence. When setting up a table, each 2-byte position in the table
corresponds to a character. To change the order in which a character is sorted,
change its 2-digit value to the same value as the character it should be sorted
equal to. For information about sorting uppercase and lowercase characters
regardless of their case, the QCASE256 table in library QUSRSYS is provided
for you.