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Pig >> mail # user >> CONCAT(null, "something") == NULL ?


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Yang 2012-11-02, 22:09
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Alan Gates 2012-11-02, 22:33
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Re: CONCAT(null, "something") == NULL ?
Hi Alan,

Recently, I have seen several similar confusions about nulls in Pig. For
example, here is another discussion:
https://issues.apache.org/jira/browse/PIG-3021.

We are documenting them, but apparently, many users find it confusing. I am
wondering if there is anything that we can do better.

Thanks,
Cheolsoo

On Fri, Nov 2, 2012 at 3:33 PM, Alan Gates <[EMAIL PROTECTED]> wrote:

> To give some context, the null semantics in Pig follow SQL's.  In SQL,
> null is viral, so any operation with null results in null.  The idea is
> that null means unknown, not empty.  So concat('x', unknown) = unknown.
>
> Alan.
>
> On Nov 2, 2012, at 3:09 PM, Yang wrote:
>
> > looks a more intuitive result should be "something" , right?
> >
> > but on my system it gave null
>
>
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Yang 2012-11-05, 17:15
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Alan Gates 2012-11-05, 16:16
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Jonathan Coveney 2012-11-05, 18:01
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Cheolsoo Park 2012-11-02, 22:14