Bug #604: string join problem
Erol Ozcan (erol@infotron.com.tr) reports a bug with a severity of 2
The lower the number the more severe it is.
Short Description
string join problem
Long Description
I have a major problem with string joining in sql query in Postgresql 7.1.3. It is always return null string if any of column has null value.
I attached some example code sources to explain the problem.
Sample Code
CREATE TABLE phone
(
phn_id INT NOT NULL PRIMARY KEY,
phn_country INT NULL,
phn_area INT NULL,
phn_number INT NULL,
phn_ext INT NULL
);
INSERT INTO phone VALUES( 30, 90, 216, 4921002, NULL );
SELECT '+'|| phn_country||'-'||phn_area||'-'||phn_number FROM phone WHERE phn_id=30;
?column?
-----------------
+90-216-4921002
(1 row)
SELECT '+'||phn_country||'-'||phn_area||'-'||phn_number||' ext:'||phn_ext FROM phone WHERE phn_id=30;
?column?
----------
(1 row)
No file was uploaded with this report
pgsql-bugs@postgresql.org writes:
I have a major problem with string joining in sql query in Postgresql 7.1.3. It is always return null string if any of column has null value.
This is not a bug. SQL92 6.13 general rule 2a saith:
a) If either S1 or S2 is the null value, then the result of the
<concatenation> is the null value.
Consider using something like
COALESCE(col1,'') || COALESCE(col2,'') || ...
if you want to treat NULLs as empty strings. Also consider whether you
shouldn't have stored the fields as empty strings in the first place.
NULL and empty string are not at all the same thing; if your data design
treats them as interchangeable then your design is broken, IMHO.
regards, tom lane
Tom Lane wrote:
pgsql-bugs@postgresql.org writes:
I have a major problem with string joining in sql query in Postgresql 7.1.3. It is always return null string if any of column has null value.
This is not a bug. SQL92 6.13 general rule 2a saith:
a) If either S1 or S2 is the null value, then the result of the
<concatenation> is the null value.Consider using something like
COALESCE(col1,'') || COALESCE(col2,'') || ...
if you want to treat NULLs as empty strings. Also consider whether you
shouldn't have stored the fields as empty strings in the first place.
NULL and empty string are not at all the same thing; if your data design
treats them as interchangeable then your design is broken, IMHO.regards, tom lane
Thanks for the reply. COALESCE is working good, however, I wrote a PL/pgSQL procedure to get more proper results.
Best Regards,
--
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Erol Ozcan mailto:erol@infotron.com.tr
Software Engineer http://www.infotron.com.tr
Tel: +90-216-4921002
info(+)TRON A.S Istanbul/Turkey
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