COBOL Manual for TNS and TNS/R Programs

Procedure Division Verbs
HP COBOL Manual for TNS and TNS/R Programs—522555-006
9-234
SORT
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INPUT PROCEDURE phrase
If the INPUT PROCEDURE phrase appears, the input phase executes an
implicit PERFORM procedure-group statement (where procedure-
group is procedure name, optionally followed by THROUGH or THRU and
another procedure name). The sort input procedure thereby specified is
responsible for releasing the records to be sorted by one or more executions of
RELEASE statements. The sort input procedure must not open a file specified
by outfile. Control automatically returns to the sort operation after
completing the execution of the implicit PERFORM statement.
The range of the implicit procedure must not cause the execution of a MERGE,
RETURN, or SORT statement or a RELEASE statement that references any
sort or merge file other than the one identified by sd-name.
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Sort Phase of Execution
The sort phase reorders the records within the sort file according to their sort key
values. The records of sd-name are first sorted in accordance with their values for
the most significant (first listed) sort key. When two or more records have equal
values for the current sort key, that group of records is then sorted in accordance
with the record values for the next most significant key, and so on. When two or
more records contain equal values for all sort keys, their final order within the sort
file depends on the DUPLICATES phrase. If DUPLICATES is specified, their order
will be the order in which they were released to the sort file. If DUPLICATES is not
specified, their order is arbitrary.
The key s are listed from left to right within the SORT statement in order of
decreasing significance, without regard to how the list of keys is divided into
ASCENDING KEY or DESCENDING KEY phrases; therefore, the data item
specified by the first key is the most significant sort key, and the data item
specified by the last key is the least significant sort key.
The ordering implied by a sort key depends upon its KEY phrase:
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When the sort key is specified in an ASCENDING KEY phrase, the sorted
sequence is from the record having the lowest value in the sort key data item
to the record having the highest value in the sort key data item.
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When the sort key is specified in a DESCENDING KEY phrase, the sorted
sequence is from the record having the highest value in the sort key data item
to the record having the lowest value in the sort key data item.
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In both cases, the determination of which value is higher is made according to
the rules for comparison of operands in a relation condition.
The collating sequence that applies to the comparison of nonnumeric sort key data
items is the one specified by the alphabet-name in the COLLATING SEQUENCE
phrase. When this phrase is not specified, the program collating sequence applies.