Determining if a string macro variable does not exist in a column of a dataset in SAS

I have a string macro variable %let string=abc and a dataset column that contains values def ghi.

How do I use datastep to run &string. through the entire column to create an indicator macro variable to show that abc does not exist in the column?

You can use call symput() to create a macro variable in a data step.

The code below creates a macro variable which has value 0 if the string is not found in the data, and value 1 if the string is found:

* create example data;
data have;
    input var1 $;
    datalines;
def
ghi
;
run;

%let string=abc;

* data step to create variable STRING_CHECK which equals 1 if HAVE contains 'abc', and equals 0 otherwise;
data _null_;
    set have (keep=var1) end=last_obs;
    retain flag 0;
    if var1 = "&string" then flag=1;
    * at end of data set, create the required macro variable;
    if last_obs then call symput('string_check',left(flag));
run;

%put &=string_check;