Re: BUG #7899: allow key word as alias in subquery but Can't reference it in outer query

I have get the description of this behaviour from doc 7.3.2
http://www.postgresql.org/docs/devel/static/queries-select-lists.html#QUERIES-COLUMN-LABELS
.

from the error message now,I think syntax error may emmit by the
parser,parser error make it hard to get the really condition such as the
second token ‘end’ is a select item from a select statement.

thanks

2013/2/22 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>

> "=?ISO-8859-1?B?Sm92?=" <amutu(at)amutu(dot)com> writes:
> > xxx=# select end from (select 1 as end) t;
> > ERROR: syntax error at or near "end"
> > LINE 1: select end from (select 1 as end) t;
> > ^
>
> You need to double-quote the outer use of "end", viz
>
> regression=# select "end" from (select 1 as end) t;
> end
> -----
> 1
> (1 row)
>
> In the context with "as", Postgres can tell the word is meant as a
> column identifier not a keyword, but there's no way for it to know that
> in the outer usage.
>
> > I think use key word as alias should get a error message such as
> $key_word
> > is Key Word,should not be used as identifier bla bla,so for some complex
> > query error user can save a lot of time.
>
> Well, yours is the first complaint we've ever had in that direction,
> whereas we used to get a lot of complaints in the opposite direction,
> back when we didn't allow keywords to be used for column names.
> So I doubt we'll change it. It is an interesting gotcha though :-(
>
> regards, tom lane
> .
>
>

--
Jov
blog: http:amutu.com/blog <http://amutu.com/blog>