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发表于 2010-11-17 14:03:45
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跟crackman做sas adv认证试题(10)
From crackman's blog on Baidu
<p><font size="4" face="宋体">Given the SAS data set WORK.ONE: <br>
<br>
Rep Cost <br>
----- ---- <br>
SMITH 200 <br>
SMITH 400 <br>
JONES 100 <br>
SMITH 600 <br>
JONES 100 <br>
<br>
The following SAS program is submitted; <br>
<br>
proc sql; <br>
select <br>
Rep, <br>
avg(Cost)<br>
from WORK.ONE<br>
order by Rep<br>
; <br>
quit; <br>
<br>
Which result set would be generated? </font></p>
<p><br>
<font size="4" face="宋体"> A.<br>
JONES 280 <br>
JONES 280 <br>
SMITH 280 <br>
SMITH 280 <br>
SMITH 280 <br>
<br>
B.<br>
JONES 600 <br>
SMITH 100 <br>
<br>
C.<br>
JONES 280 <br>
SMITH 280 <br>
<br>
D.<br>
JONES 100 <br>
JONES 100 <br>
SMITH 600 <br>
SMITH 600 <br>
SMITH 600 </font></p>
<p><font size="4" face="宋体">这里答案为A。<br>
SQL语句中,AVG计算的是一列的平均值,所以AVG只有一个值,答案选择A。<br>
如果改成为:</font></p>
<p><font size="4" face="宋体">proc sql; <br>
select <br>
Rep, <br>
avg(Cost)<br>
from WORK.ONE<br>
group by Rep<br>
order by Rep<br>
; <br>
quit; </font></p>
<p><font size="4" face="宋体">结果会如何呢?</font></p>
<p><font size="4" face="宋体">示例程序:<br>
data crackman;<br>
input rep $ cost@;<br>
datalines;<br>
SMITH 200 <br>
SMITH 400 <br>
JONES 100 <br>
SMITH 600 <br>
JONES 100<br>
;<br>
run;<br>
proc sql; <br>
select <br>
Rep, <br>
avg(Cost)<br>
from WORK.CRACKMAN<br>
order by Rep<br>
; <br>
quit; </font></p> <a href="http://hi.baidu.com/crack%5Fman/blog/item/8ea000278f72dc5e9358074b.html">阅读全文</a>
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