Re: conditional query in where has name collision. bug?

>>>>> "bill" == bill wilson <bill(dot)wilson(dot)home(at)gmail(dot)com> writes:

bill> This a toy example from a 'upsert' script that appends new data:
bill> select a from (select 1 as a) as t1 where not exists (select
bill> true from (select 2 as a) t2 where a=a) ;
bill> a
bill> ───
bill> (0 rows)

bill> Please tell me this a bug. We can see in the first query
bill> without naming the tables that 'a=a' uses table t2 for both
bill> columns.

Of course it's not a bug. The column "a" in the inner scope hides the
column "a" in the outer scope, as explicitly required by the spec
(6.6 <identifier chain> in sql2008).

--
Andrew (irc:RhodiumToad)