PG Bug reporting form <noreply@postgresql.org> writes:
> 1. The following code is successfully executed although it has incorrect
> syntax: there must be comma (,) between _n and _s in 'into' section.
> select 1, 'string1', 'string2'
> into _n _s;
I believe this is being read the same as
select 1, 'string1', 'string2' _s into _n;
That is, the lack of a comma causes the INTO sub-clause to end,
and then _s is taken as an AS-less column label. As the manual
explains, for backwards-compatibility reasons we allow INTO to be
embedded anywhere in the command, even though that leads to
surprising-looking cases like this one.
As for the question of why you don't get an error for the wrong
number of INTO targets, again that's backwards compatibility.
There's a "strict_multi_assignment" check you can turn on to make
it complain about that [1].
regards, tom lane
[1] https://www.postgresql.org/docs/current/plpgsql-development-tips.html#PLPGSQL-EXTRA-CHECKS