On 10/19/22 12:30, Mark Raynsford wrote:
On 2022-10-19T11:58:07 -0700
"David G. Johnston" <david.g.johnston@xxxxxxxxx> wrote:
On Wed, Oct 19, 2022 at 10:36 AM Mark Raynsford <co+org.postgresql@xxxxxxxx>
wrote:
insert into t (y) values (t.x * 2);
I can think of various ways to do it with multiple statements, but a
single statement would be preferable.
No, by extension of the documented constraint: "The generation expression
can refer to other columns in the table, but not other generated columns."
Hello!
Just want to confirm that I wasn't misunderstood. The documentation in
CREATE TABLE has the sentence you quoted above, and unless I'm
misunderstanding that's saying that the expression used to generate
values in GENERATED (ALWAYS AS) columns can't refer to other GENERATED
columns. That's fine, but that's not what I was asking. In the table
above, `x` is generated without references to other columns, but for
the non-GENERATED `y` value, I want to refer to the value that `x` will
have when I calculate a value for the `y` column in the INSERT
statement.
If that's not doable, that's fine, I just want to be sure. :)
create table t (
x integer not null generated always as identity,
y integer not null
);
insert into t (y) values (t.x * 2);
ERROR: invalid reference to FROM-clause entry for table "t"
LINE 1: insert into t (y) values (t.x * 2);
^
HINT: There is an entry for table "t", but it cannot be referenced from
this part of the query.
insert into t (y) values (x * 2);
ERROR: column "x" does not exist
LINE 1: insert into t (y) values (x * 2);
^
HINT: There is a column named "x" in table "t", but it cannot be
referenced from this part of the query.
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
