This a toy example from a 'upsert' script that appends new data:
select a from (select 1 as a) as t1 where not exists (select true from (select 2 as a) t2 where a=a) ;
a
───
(0 rows)
select a from (select 1 as a) as t1 where not exists (select true from (select 2 as a) t2 where t1.a=t2.a) ;
a
───
1
(1 row)
Please tell me this a bug. We can see in the first query without naming the tables that 'a=a' uses table t2 for both columns. Luckily, the incorrect first query fails from primary key conditions in real life. This goes against the implied convention that when in doubt raise an error. It is also a very idiomatic way to to real life inserts. So, I cannot believe that I am the first to find this. The behavior reminds me of old school mysql: lets allow an int and a string to add and just cast the string as an int because that must be what the user wants and will be convenient.
