求解这个程序的答案

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data short;
input x;
datalines;
1
2
;
run;
data long;
input x;
datalines;
3
4
5
6
;
run;
data new;
set short;
output;
set long;
output;
run;


为什么生成的NEW数据集，只有4行？而且结果是  1 3 2 4 ……

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关键词：output outpu Short Lines Input 程序

不知道通过审核了没有，先自己顶下……

there exists 2 data loops,  for the data set having less obs contains only 2 obs.
In loop 1, the system read in x=1 and x=3 sequentially;
In loop 2, the system read in x=2 and x=4 sequentially.

Actually there are 3 data iterations:

_N_=1:  read the first record from short(x=1), then output;
             read the first record from long(x=3), then output;

_N_=2:  read the second record from short(x=2), then output;
             read the second record from long(x=4), then output;

_N_=3: try to read the next record from short but none available, the DATA Step stops.

嗯嗯，学习了

多谢楼上两位大神解答

双set有意思

so if switch the position of "short" and "long"

data new;
set long;
output;
set short;
output;
run;

there will be 5 obs instead of 4.