Proc SQL neT operator does not evaluate properly in WHERE - sas

Question

Can't figure out why the WHERE clause does not filter the rows selected.
The neT evaluation is correction during assignment, but not working in the WHERE clause (all 5 rows selected!)
data a;
input a $ b $; datalines;
abcd abdef
abcd abcdefg
abcdef abcd
xxyyzz .
. xxyyzz
run;
proc sql;
create table b as
select *
, a neT b as neT
, a eqT b as eqT
from a
where a neT b
;
quit;
Table B

Answer 1

You need strip
where strip(a) neT strip(b)
This is also relevant to the topic.
44 data _null_;
45 a='12';
46 b='1 ';
47 x = a eq: b;
48 z = strip(a) eq: strip(b);
49 put _all_;
50 run;
a=12 b=1 x=0 z=1 _ERROR_=0 _N_=1

Answer 2

This is confusingly documented, but may be correct behavior (though I have no idea why).
In the documentation of the SQL truncating expressions:
The Base SAS WHERE processor handles truncated comparisons differently than PROC SQL does. The Base SAS WHERE processor truncates comparisons based on the actual length of a string, even if a string includes blanks at the end. PROC SQL trims trailing blanks from the string values before it truncates comparisons. PROC SQL truncates string comparisons similar to other SQL processors that conform, in various degrees, to the INCITS/ISO/IEC/ANSI SQL:2011 Standards.
Now, this is confusing of course because the documentation says that base SAS Where would work the way you describe in the second example, i.e.:
data b;
set a;
where a ne: b;
run;
Per the documentation, that is expected to return 5 rows. However, it's unclear why the SQL where behaves this way and not the way the documentation says SQL handles things - but it's also not really surprising, as I'd always understood where to typically work the same way in both PROC SQL and the data step. You might want to try raising a track with tech support - or if you don't know how to do that, I can, to verify that this is intended behavior and not unintended.
Of course, why this is considered correct behavior (even in the data step where), I have no idea. It makes the truncating expressions basically useless for comparing variables to each other, without adding the strip or trim to both ... which is the normal behavior in other modes, anyway. I'm guessing this is some sort of backwards compatibility issue gone haywire, and I'd encourage you to create a SASWare Ballot idea to have this behavior changed.
You can work around this either as Data _Null explains - by using strip on both arguments, or trim - or, if you actually are using the neT in a column expression as well as the where, you can use calculated:
proc sql;
create table b as
select *
, a neT b as _neT
, a eqT b as _eqT
from a
where calculated _net eq 1
;
quit;