if condition dataset

[rajeshm]

in the below code if condition should not be executed but how i was able to print n varible  value? 

data _null_;
if -2 then set sashelp.class nobs=n;
call symput ('nrows',n);
run;

[andreas_lds]

All SET statements are always executed at compile time to to build the pdv, the IF -statement prevents execution at runtime, so that no observations are read.

[PeterClemmensen]

Because the n variable in nobs=n is set at compile time

[s_lassen · Accepted solution]

Two reasons:

• Actually, your SET statement IS executed. SAS interpretes anything not zero or missing as a TRUE boolean value, so "if -2" is equivalent to "if 1"
• The NOBS option sets the variable at compile time, as @PeterClemmensen already remarked.

The last reason is why you can get away with stuff like this:

data test;
  do i=1 to n;
    set x.data1 nobs=n;
    output;
    end;
run;

So the N variable is defined and set before the loop which contains the SET statement begins execution.