On 5/20/19 11:11 AM, Chuck Martin wrote:
My Google foo isn't working on this question, probably because I don't
understand the question well enough. I'm using Postgres 11.3 on Centos
7. I'm trying to insert a record in table A with a foreign key to table
B, but only where there is not already a foreign key in A to B. So
assume this simple structure:
Table A
A.key Integer
A.something text
A.Bkey Integer [foreign key to table B, column B.key
Table B (or View C)
B.key Integer
[more columns]
Thinking that it might simplify matters, I created a view to table B
that only includes records with no foreign key in Table A. But still,
after reading the documentation and Googling, I can't work out what
seems like it should be simple. Among the many things that didn't work is:
INSERT INTO A(something,A.Bkey)
VALUES ('text',
(SELECT C.key FROM C)
But this didn't work because the subquery returned more than one value.
Of course I want it to return all values, but just one per insert.
I can do this outside of Postgres, but would like to learn how to do
this with SQL.
Some examples that you can modify:
https://www.postgresql.org/docs/11/sql-insert.html
INSERT INTO films SELECT * FROM tmp_films WHERE date_prod < '2004-05-07';
WITH upd AS (
UPDATE employees SET sales_count = sales_count + 1 WHERE id =
(SELECT sales_person FROM accounts WHERE name = 'Acme Corporation')
RETURNING *
)
INSERT INTO employees_log SELECT *, current_timestamp FROM upd;
Chuck Martin
Avondale Software
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
