Use one of the following forms for BY-group processing:
BY variable(s);
BY <DESCENDING> variable(s) <NOTSORTED> <GROUPFORMAT>;
where
indicates that the
data sets are sorted in descending order (largest to smallest) by
the variable that is specified. If you have more that one variable
in the BY group, DESCENDING applies only to the variable that immediately
follows it.
names each variable
by which the data set is sorted or indexed.
Note: All data sets must be ordered
or indexed on the values of the BY variable if you process them using
the SET, MERGE, or UPDATE statements. If you use the MODIFY statement,
your data does not need to be ordered. However, your program might
run more efficiently with ordered data. All data sets that are being
combined must include the BY variable or variables. The position of
the BY variable in the observations does not matter.
specifies that observations
with the same BY value are grouped together but are not necessarily
stored in alphabetical or numeric order.
uses the formatted
values, instead of the internal values, of the BY variables to determine
where BY-groups begin and end, and therefore how FIRST.variable and
LAST.variable are assigned.
Although the GROUPFORMAT option can appear anywhere in the BY statement,
the option applies to all variables in the BY statement.
For complete information
about the BY statement, see
BY Statement in SAS Statements: Reference.