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 <t...@sss.pgh.pa.us> > "=?ISO-8859-1?B?Sm92?=" <am...@amutu.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>
