太大的选择需要输入很多条件，浪费时间也浪费运行时间

原作者年代有点久远，我在备考时候也遇到了这个问题，然后就google了一下。以后还有人需要问答，大家看一下吧，可靠答案。
貌似意思就是如果是那种0/1逻辑条件的情况下，SELECT 比IF更有效。
When you have a long series of mutually exclusive conditions, using a SELECT group is more efficient than using a series of IF-THEN statements because CPU time is reduced. Large numbers of conditions make a SELECT group more efficient than IF-THEN/ELSE statements because CPU time is reduced. SELECT groups also make the program easier to read and debug.