proc sql error message

[Bal23]

proc sql; create table dadkid4 as select *, (dads.famid=faminc.famid) as indic, (dads.famid ~=.) as dadind, (faminc.famid ~=.) as famind, coalesce(dads.famid, faminc.famid) as fid from dads full join faminc on dads.famid=faminc.famid; quit;

ERROR: Expression using not equals (^=) has components that are of different data types.

ERROR: Expression using not equals (^=) has components that are of different data types.

two IDs are char variables, there should be not a problem?

I then  convert both to numberical variables, still same error message.

any idea how to fix it?

Thanks.

[Doc_Duke · Accepted solution]

The missing value indicator for a character variable is a single space, e.g. ' ' (two quotes with one space in between).

http://support.sas.com/documentation/cdl/en/lrcon/62955/HTML/default/viewer.htm#a002316433.htm