Re: Why the "UPDATE tab SET tab.col" is invalid?

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От Tom Lane
Тема Re: Why the "UPDATE tab SET tab.col" is invalid?
Дата
Msg-id 1466.1460036567@sss.pgh.pa.us
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Ответ на Why the "UPDATE tab SET tab.col" is invalid?  ("postgres_sure"<postgres_sure@163.com>)
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"postgres_sure"<postgres_sure@163.com> writes:
> I found "Do not include the table's name in the specification of a target column
>                  — for example, UPDATE tab SET tab.col = 1 is invalid." in the documentation. 

> Some people usually like to update table by alias. They want to add this feature.

Sorry, but we aren't ever going to accept such a patch, because it would
introduce an unavoidable ambiguity: is "SET a.b = " meant to be an
assignment to column b of table a, or is it meant to be an assignment to
sub-field b of composite column a?

Yeah, we could invent some resolution rules to deal with that, but
better to just not add the nonstandard syntax (and it IS nonstandard,
SQL:2011 has nothing about it) in the first place.
        regards, tom lane



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