how to check if a dataset has observation or not?

shiyiming

e.g.:
data a;
input x;
cards;
;
run;
data b;
input x;
cards;
1
;
run;
how can I check a dataset has observation or not?
I am trying open() function, but I do not know how to use it, could anyone help? Thanks a lot.

shiyiming

/*检查数据中存在的变量*/
data _null_;
   a=open('sashelp.class');     
   b=varnum(a,'age'); /*变量age存在的话，b不为0*/
   c=varnum(a,'sex');
   if b=0 then put 'Variable does not exist';
       else put 'Variable is located in column ' b+(-1) '.';  
   if c=0 then put 'Variable does not exist';
       else put 'Variable is located in column ' c+(-1) '.';
run;
/*检查逻辑库中存在的数据*/
data _null_;
   d=exist('sashelp.class','data'); /*data为数据类型，也可以为view等形式，存在默认为1*/
   if d=1 then put 'data set exists';
   else put 'data set does not exist';
run;

shiyiming

%let c= %sysfunc(open(work.a, i)) /*a is your data set*/
%let records= %sysfunc(attrn(&c, NOBS));

%PUT &RECORDS

shiyiming

Note: the libname and dataset name must in uper cases for all leters;
proc sql;
select nobs from dictionary.tables
where libname eq "WORK" and memname eq "A";
quit;

or :

Proc SQL;
select nobs from sashelp.vtable where libname eq "WORK" and memname eq "A";
Quit;