Which statement is true regardin

Which statement is true regarding the default behavior of the ORDER BY clause?

A. In a character sort,   the values are case- sensitive. 

B. NULL values are not considered at all by the sort operation.  

C. Only those columns that are specified in the SELECT list can be used in the ORDER BY clause. 

D. Numeric values are displayed from the maximum to the minimum value if they have decimal positions. 

Answer: A

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12837221

A对，在字符排序中，是区分大小写的。

B错，对于升序排序，空值显示在最后，对于降序排序，则显示在最前面。即NULL是被考虑的

C错，可以指定不在select列中的字段来排序。

D错，不管是否小数，都是按照数值的大小来升序或降序排列。