SAS程序疑问

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54.Consider the following data step:

data WORK.TEST;
    set SASHELP.CLASS(obs=5);
    retain City 'Beverly Hills';
    State='California';
run;

A. The RETAIN statement is fine, but the value of City will be truncated to 8

bytes as the LENGTH statement has been omitted.

    B. Both the RETAIN and assignment statement are being used to initialize new

variables and are equally efficient. Method used is a matter of programmer preference.

     C. The assignment statement is fine, but the value of City will be truncated

to 8 bytes as the LENGTH statement has been omitted.

     D. City's value will be assigned one time, State's value 5 times.

Answer: D

对D表示不懂

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关键词：sas程序 assignment Programmer Preference california 程序 efficient following matter

RETAIN Statement is compile-time only

赋值语句在执行过程中执行，retain语句在编译阶段赋值一次，执行的时候只是直接从pdv输出到output dataset而已。

hcydlee 发表于 2012-8-7 15:34
赋值语句在执行过程中执行，retain语句在编译阶段赋值一次，执行的时候只是直接从pdv输出到output 大taset而 ...

哇，够深奥，这是哪里的知识啊？！

好解答啊