Differentiate Between Zero-Length String and NULL Column Values

Hi All,

Small problem with 8.2.1, I have a temp table of basic stock details:
CREATE TEMP TABLE tmpstk
(
code varchar(6),
description varchar(38),
grp varchar(4),
brand text,
style text,
supplier varchar(6),
supplier_code text,
wholesale numeric(10,2),
retail numeric(10,2),
ean varchar(13)
)
WITHOUT OIDS;

This table is populated using a COPY query – works OK. If I try the
following query:
SELECT * FROM tmpstk
I get what I expect, almost 8000 rows including rows similar to the
following:
"401514","EQUINADE_SHOWSILK_SHAMPOO_5L","3209","EQUINADE","SHAMPOO","EQUEST"
,"401514","0.00","0.00","0.00","0.00","10.00","9329028056594"
"401600","A/DRESS_SHAMPOO_TEA_TREE_OIL_500ML","3208","AUSTRALIAN_DRESSAGE","
SHAMPOO","EQUEST","401600","0.00","0.00","0.00","0.00","10.00",""

The second row (401600) is what I’m interested in for this particular
problem. The problem is when I try and add a WHERE clause:
SELECT * FROM tmpstk WHERE ean = '';
SELECT * FROM tmpstk WHERE TRIM(ean) = '';
SELECT * FROM tmpstk WHERE ean = NULL;
None of the above queries return any rows.

What am I doing wrong? It should return the 401600 row above, along with
several hundred other rows. I have attached the bash script that actually
does this processing.

Help is much appreciated.
Cheers,
-p

Phillip Smith
IT Coordinator
Weatherbeeta P/L
AUSTRALIA
 
E. phillip(dot)smith(at)NO-SPAM(dot)weatherbeeta(dot)com(dot)au

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