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The online doc (SAS SQL Procedure User's Guide) says that "to be compatible
with the rest of SAS, PROC SQL treats missing values the same as blanks or
zero values, and considers all three to be null values".
(http://support.sas.com/onlinedoc/913/getDoc/en/sqlproc.hlp/a001409512.htm)
On the numeric side, that of course mischaracterizes the "rest of" SAS, and
is not true.
Demonstration:
data test;
do value = 1,0,.,-1; output; end;
run;
proc sql;
select case when value is null then put(value,2.) || ' is null.'
else put(value,2.) || ' is not null.'
end
from test;
quit;
This yields:
1 is not null.
0 is not null.
. is null.
-1 is not null.
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