Given the SAS data set WORK.TEMPS:
| Day | Month | Temp |
| 1 | May | 75 |
| 15 | May | 70 |
| 15 | June | 80 |
| 3 | June | 76 |
| 2 | July | 85 |
| 14 | July | 89 |
The following program is submitted:
proc sort data=WORK.TEMPS;
by descending Month Day;
run;
proc print data=WORK.TEMPS;
run;
Which output is correct?
A.
| Obs | Day | Month | Temp |
| 1 | 2 | July | 85 |
| 2 | 14 | July | 89 |
| 3 | 3 | June | 76 |
| 4 | 15 | June | 80 |
| 5 | 1 | May | 75 |
| 6 | 15 | May | 70 |
B.
| Obs | Day | Month | Temp |
| 1 | 1 | May | 75 |
| 2 | 2 | July | 85 |
| 3 | 3 | June | 76 |
| 4 | 14 | July | 89 |
| 5 | 15 | May | 70 |
| 6 | 15 | June | 80 |
C.
| Obs | Day | Month | Temp |
| 1 | 1 | May | 75 |
| 2 | 15 | May | 70 |
| 3 | 3 | June | 76 |
| 4 | 15 | June | 80 |
| 5 | 2 | July | 85 |
| 6 | 14 | July | 89 |
D.
| Obs | Day | Month | Temp |
| 1 | 15 | May | 70 |
| 2 | 1 | May | 75 |
| 3 | 15 | June | 80 |
| 4 | 3 | June | 76 |
| 5 | 14 | July | 89 |
| 6 | 2 | July | 85 |
注解：DESCENDING只作用于紧跟着它的那一个变量，所以输出的结果应当先按Month降序排列，相同的Month再按Day升序排列。Month是字符型，所以按照英文字母的顺序倒序排列。注意，SAS并不知道May是5月，June是6月，SAS只知道May的第一个字母是M，而June的第一个字母是J。字符型变量的排序在采用不同编码表的操作系统中略有不同。
采用ASCII编码的系统，例如Windows，Linux和MAC OS中，各字符从小到大的排列顺序为：
空格 ! ” # $ % & ‘ ( ) * + , – . /0 1 2 3 4 5 6 7 8 9 : ; < = > ? @
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z[ ] ˆ_
a b c d e f g h i j k l m n o p q r s t u v w x y z { } ~
采用EBCDIC编码的系统，例如z/OS，各字符从小到大的排列顺序为：
空格 . < ( + | & ! $ * ) ; ¬ – / , % _ > ?: # @ ‘ = “
a b c d e f g h i j k l m n o p q r ~ s t u v w x y z
{ A B C D E F G H I } J K L M N O P Q R S T U V W X Y Z
0 1 2 3 4 5 6 7 8 9