On 12/9/25 18:29, David G. Johnston wrote:
On Tue, Dec 9, 2025 at 10:14 AM Thiemo Kellner
<[email protected]> wrote:
I feel, you meant to say, the subquery does not return any record
which is not the same as returns NULL.
For a scalar subquery the final output of a zero-row query is the null
value.
To me, it does not look like that (please note the empty line in the
last example). Can you point me to the documentation saying that 0 rows
is sometimes equal to 1 row?
postgres=# select * from pg_user;
usename | usesysid | usecreatedb | usesuper | userepl | usebypassrls
| passwd | valuntil | useconfig
----------+----------+-------------+----------+---------+--------------+----------+----------+-----------
postgres | 10 | t | t | t | t |
******** | |
(1 row)
postgres=# select usename from pg_user where false;
usename
---------
(0 rows)
postgres=# select null as usename from pg_user;
usename
---------
(1 row)
