When you use the LIBNAME statement
to associate a libref with PC files data, you might observe some behavior
that differs from that of normal SAS LIBREFS. Because these LIBREFS
refer to database and workbook objects, such as tables, they are stored
in a format that differs from the format of normal SAS data sets.
This is helpful to remember when you access and work with PC files
data.
For example, you can
sort the observations in a normal SAS data set and store the output
to another data set. However, in a Microsoft Access database, sorting
data has no effect on how it is stored. Because your data might not
be sorted in the external file, you must sort the data at the time
of query. When you sort PC files data, the results might vary. Depending
on whether the external spreadsheet or database places data has NULL
values. If the sort encounters NULL values, are they listed at the
beginning or end of the result set. NULL values are translated in
SAS to missing values.