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Re: BUG #6064: != NULL, <> NULL do not work [sec=UNCLASSIFIED]

From: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>
To: "Pilling, Michael" <Michael(dot)Pilling(at)dsto(dot)defence(dot)gov(dot)au>
Cc: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #6064: != NULL, <> NULL do not work [sec=UNCLASSIFIED]
Date: 2011-06-20 00:39:55
Message-ID: 4DFE96DB.9050207@postnewspapers.com.au (view raw or flat)
Thread:
Lists: pgsql-bugs
On 20/06/2011 8:30 AM, Pilling, Michael wrote:

> I was looking at that page but didn't read the detail because I thought
> the information was in the table and the detail was just textual examples.

I do think that adding "IS DISTINCT FROM" and "IS NULL / IS NOT NULL" to 
the summary table would be helpful, with a superscript * linking to  the 
note about null handling below.

In general, though, there's only so much information that can be 
condensed into the brief summary and tables.

Reading the documentation in detail is a really, really good idea. It'll 
tell you a lot about Pg and about SQL in general. I've generally found 
it really helpful and not at all long-winded. It's pretty much how I 
learned to use relational databases.

In this case the documentation even has a big box-out saying:

"Tip: Some applications might expect that expression = NULL returns true 
if expression evaluates to the null value."

... that carries on to explain about NULLs.


-- 
Craig Ringer

Tech-related writing at http://soapyfrogs.blogspot.com/

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