将插入结果插入另一个表

Question

With PostgreSQL, given the following tables :

CREATE TABLE events (
  id BIGSERIAL PRIMARY KEY,
  timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL,
);

CREATE TABLE event_details (
  uuid UUID NOT NULL,
  signal_strength SMALLINT NOT NULL,
  event_id INTEGER REFERENCES events (id) ON DELETE RESTRICT,
  PRIMARY KEY (event_id)
);

To insert an event, I must insert the event details first, then insert the "generic" event after, linking with the event details. I have built this query to do this :

INSERT INTO event_details VALUES ('B9056867-459D-4F0B-8627-7456C880F54B', 50, (INSERT INTO events VALUES (DEFAULT, '2014-03-21 15:37:44.683081-04') RETURNING id));

But I get this error : ERROR: syntax error at or near "INTO"

So I can't insert a value with an INSERT INTO like I would do with a SELECT . How can I forward the newly created row id into the foreign key column of event_details?

There may be a lot of these queries when the system will be running, so I would like to avoid retrieving the id back in my code (in NodeJS) and then do the second INSERT in a separate statement.

Thanks!

PS : I simplified the SQL of the tables, but I have some good reasons to separate event_details with events (there are many event types with different details).

[edit]

The right way to do it, in this situation, is :

WITH new_event AS (INSERT INTO events VALUES (DEFAULT, '2014-03-21 15:37:44.683081-04') RETURNING id) INSERT INTO event_details VALUES ('B9056867-459D-4F0B-8627-7456C880F54B', 50, (SELECT id FROM new_event LIMIT 1));

Thanks to Jaffar's answer for this solution!

Answer 1

PostgreSQL has such an extended interpretation of the VALUES clause that it may be used as a subquery by itself.

So you may express your query in this form:

WITH new_invoice AS (
    INSERT INTO ...
    RETURNING id
),
v(a,b,c,d) AS (values
  ($27,$28,$29,$30),
  ($31,$32,$33,$34),
  ...
)
INSERT INTO invoiceItems (invoice_id, name, qty, price, description)
 SELECT new_invoice.id, a,b,c,d FROM v, new_invoice;

That assumes you want to insert the cartesian product of new_invoice and the values, which mostly makes sense if new_invoice is actually a single-row value.

Answer 2

You must separate the queries since an insert-subquery is not a valid value expression:

http://www.postgresql.org/docs/9.3/static/sql-expressions.html

Or you can make a stored procedure. That reduces the overhead.