The variable names in
the variable-list are separated
by spaces.
The ordering is hierarchical.
For example, ORDERBY=(A B) specifies ordering by the values of variable
B within the ordered values of variable A. The specified variables
must exist and cannot be specified as partitioning variables. The
order is determined based on the raw value of the variables and uses
locale-sensitive collation for character variables. By default, values
are arranged in ascending order. You can specify descending order
by preceding the variable name in the variable-list with
the keyword DESCENDING.