测试变量是否存在

open()

varnum()

varnum()

data try; 
    input var1 var2 var3;
    datalines;
    7 2 2
    5 5 3
    7 2 7
; 

data try2; 
    set try;
    if _n_ = 1 then do; 
        dsid=open(\'try\'); 
        if varnum(dsid,\'var4\') = 0 then var4 = .; 
        rc=close(dsid);
    end;
    drop rc dsid;    
run;

data try2;
    set try;
    var4 = coalesce(var4,.);
run;

var4

data try; 
    input var1 var2 var3;
    datalines;
    7 2 2
    5 5 3
    7 2 7
; 

data try2; 
    set try; 
    var4 = var4; 
run;

attrib

    data try; 
input var1 var2 var3;
datalines;
7 2 2
5 5 3
7 2 7
; 

    data try2; 
length var4 $20;
length var5 8;
set try; 
var4 = var4; 
if var4 = \' \' then var4 = \'Not on Source File\';
run;