连续使用两个set之后的结果

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data one;
input x y$;
cards;
1 Groucho
3 Harpo
3 Kart
;
data two;
input x z$;
cards;
2 Chico
4 Zeppo
;
data three;
set one;
set two;
run;
proc print data=three;
run;

连续用两个set之后结果输出十分奇怪……                                                    Obs    x       y         z                                                    1     2    Groucho    Chico                                                    2     4    Harpo      Zepposet的编译和执行原理是怎样的呢?是不是后一次的会覆盖上一次的结果？

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关键词：Set cards Three Input print one 连续

In data loop 1(_N_=1):
x=1 y=Groucho z=  _ERROR_=0 _N_=1
x=2 y=Groucho z=Chico _ERROR_=0 _N_=1
In data loop 2(_N_=2):
x=3 y=Harpo z=Chico _ERROR_=0 _N_=2
x=4 y=Harpo z=Zeppo _ERROR_=0 _N_=2
In data loop 3(_N_=3):
x=3 y=Kart z=Zeppo _ERROR_=0 _N_=3

data three;
set one;
put _all_;
set two;
put _all_;
run;

In every loop, the variable's value will be replaced by the non-default new value.

davil2000 发表于 2012-11-11 21:14
In every loop, the variable's value will be replaced by the non-default new value.

Thank you~but it seems that the data loop 3 won't do because the pointer will stop after reading the obs 2 in the dataset two. The print result also presents only two obs.....

若水烟寒 发表于 2012-11-11 21:40
Thank you~but it seems that the data loop 3 won't do because the pointer will stop after reading t ...

data three;
set one;
put _all_;
output;
set two;
put _all_;
output;
run;
proc print ;
run;

The results will be as follows:

Obs    x    y            z

1     1    Groucho
2     2    Groucho    Chico
3     3    Harpo      Chico
4     4    Harpo      Zeppo
5     3    Kart       Zeppo

data three;
set one;
put _all_;
output;
set two;
put _all_;
/*output;*/
run;
proc print ;
run;

The results will be as follows:


Obs    x    y            z

  1     1    Groucho
  2     3    Harpo      Chico
  3     3    Kart       Zeppo

data three;
put _all_;
set one;
put _all_;
/*output;*/
set two;
put _all_;
output;  /*This is always an implicit statement when there is no same statement ahead*/
run;
proc print ;
run;

the resulsts will be as follows:

Obs    x       y         z

1     2    Groucho    Chico
2     4    Harpo      Zeppo

For data set two, there exist no obs corresponding to _N_=3.  the data loop will leave out here. so the results will be only 2 obs.

By default, every DATA step contains an implicit OUTPUT statement at the end of each iteration that tells SAS to write observations to the data set or data sets that are being created.

Placing an explicit OUTPUT statement in a DATA step overrides the automatic output, and SAS adds an observation to a data set only when an explicit OUTPUT statement is executed.

Once you use an OUTPUT statement to write an observation to any one data set, however, there is no implicit OUTPUT statement at the end of the DATA step. In this situation, a DATA step writes an observation to a data set only when an explicit OUTPUT executes.

You can use the OUTPUT statement alone or as part of an IF-THEN or SELECT statement or in DO-loop processing.

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