Re: group by can use alias from select list but not the having clause

hape Hape <postgres-hape@gmx.de> writes:
> works (how does the group by know about otto if the sequence is done as
> described above?)

This is intentional and documented, eg
https://www.postgresql.org/docs/current/sql-select.html#SQL-GROUPBY
says

    An expression used inside a grouping_element can be an input column
    name, or the name or ordinal number of an output column (SELECT list
    item), or an arbitrary expression formed from input-column values.

whereas the discussion of HAVING does not mention allowing output
columns.  The reason for this is mainly that it'd seldom be useful
for a HAVING expression to be just a bare column reference, but
as soon as you write something that's not a bare column reference,
the output-column special case is disallowed anyway.