VMS Help SORT, Specification File Qualifiers, /KEY, Full Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    If you are sorting on the entire record using character data, you
    do not need to specify your key field. Otherwise, specify a /KEY
    qualifier for each of the keys, in the order of their priority.
    You can sort on as many as 255 key fields.

    There are three ways to use the /KEY qualifier:

    o  To identify the key field name.

    o  To identify the key field name and to specify sorting order.
       In this case, enclose the field name and the order option in
       parentheses.

    o  As a conditional qualifier, to change the order of records
       in the output file. First, specify a condition name in a
       /CONDITION qualifier, and set up a test for what meets
       that condition. Then, specify the relative order in a /KEY
       qualifier of the form:

       /KEY=(IF condition-name THEN value ELSE value)

       You can use any values to specify the relative order of the
       records.