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Re: Bug #604: string join problem

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: erol(at)infotron(dot)com(dot)tr, pgsql-bugs(at)postgresql(dot)org
Subject: Re: Bug #604: string join problem
Date: 2002-02-26 15:35:06
Message-ID: 29880.1014737706@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
pgsql-bugs(at)postgresql(dot)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

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