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From: "Amir Rohan" <amir.rohan@mail.com>
To: "David G. Johnston" <david.g.johnston@gmail.com>
Cc: "pgsql-docs@postgresql.org" <pgsql-docs@postgresql.org>
Subject: Re: Docs claim that "select myTable.*" wildcard won't let
 you assign column names
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Date: Tue, 22 Sep 2015 03:04:53 +0200
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On Monday, September 21, 2015, Amir Rohan <amir.rohan@mail.com> wrote:

 
>> From http://www.postgresql.org/docs/9.4/static/sql-select.html[http://www.postgresql.org/docs/9.4/static/sql->> select.html] (and previous version too):
>> 
>>   ##SELECT List
>> 
>>     <...>
>>     Instead of an expression, * can be written in the output list as a shorthand for all the columns of the 
>>     selected rows.
>>     Also, you can write table_name.* as a shorthand for the columns coming from just that table. In these 
>>     cases it is not possible to specify new names with AS; the output column names will be the same as the 
>>     table columns' names.
>>  
>> But, the docs elsewhere feature a query example show the use of a wildcard for columns
>> as well as allowing you to assign names to as many of the leading columns as you wish:
>>  
>> 
>> WITH T0 as ( SELECT 1,2,3 )
>> SELECT T0.* from T0 as T0(foo,bar) ;<...>

On Monday, September 21, 2015, David G. Johnston wrote:

> Neither of those examples is:
>  
> SELECT * AS "how would one alias this?" FROM table
>  
> So what's your point? 
 
My point is that "In these cases it is not possible to specify new names with AS" is misleading because
it *is* possible and useful, but requires syntax which isn't clearly shown (if at all) where I'd expect it.
I think that could be improved.

> Obviously you can alias stuff before it makes its way into a select-list that refers to it using *
 
"obvious" to whom? probably not to someone who's level of SQL mastery has brought him/her to reading
the exciting "SELECT" documentation. I do see your point though, in the grammar the "AS" in my example
belongs not to `output_name ` but to `from_item`. So this syntax is hidden away behind the `column_alias` 
production.
 
> In this case the FROM clause is what is being aliased.  It is documented though I'd need to look to 
> identify the specific location.
 
This belongs in the page describing SELECT, and though I've looked I haven't found it. If I'm wrong (
I did look again just now), please correct me.
 
Amir 
 
 
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