CODEWITHSUNDEEP
sqlpostgresql
Oak
Oak

Reputation: 105

PostgreSQL - Insert data into multiple tables simultaneously

I am having a data insertion problem in tables linked by foreign key. I have read in some places that there is a "with" command that helps in these situations, but I do not quite understand how it is used.

I would like to put together four tables that will be used to make a record, however, that all the data were inserted at once, in a single query, and that they were associated with the last table, to facilitate future consultations. Here is the code for creating the tables:

    CREATE TABLE participante
     (
       id serial NOT NULL,
       nome character varying(56) NOT NULL,
       CONSTRAINT participante_pkey PRIMARY KEY (id),
     );

    CREATE TABLE venda
    (
      id serial NOT NULL,
      inicio date NOT NULL,
      CONSTRAINT venda_pkey PRIMARY KEY (id)
    );

    CREATE TABLE item
    (
      id serial NOT NULL,
      nome character varying(256) NOT NULL,
      CONSTRAINT item_pkey PRIMARY KEY (id)
    );


    CREATE TABLE lances_vendas
    (
      id serial NOT NULL,
      venda_id integer NOT NULL,
      item_id integer NOT NULL,
      participante_id integer NOT NULL,
      valor numeric NOT NULL,
      CONSTRAINT lance_vendas_pkey PRIMARY KEY (id),
      CONSTRAINT lances_vendas_venda_id_fkey FOREIGN KEY (venda_id)
        REFERENCES venda (id),
      CONSTRAINT lances_vendas_item_id_fkey FOREIGN KEY (item_id)
        REFERENCES item (id),
      CONSTRAINT lances_vendas_participante_id_fkey FOREIGN KEY (participante_id)
        REFERENCES participante (id)
    );

Upvotes: 10

Views: 13484

Answers (3)

Laurenz Albe
Laurenz Albe

Reputation: 246083

The idea is to write WITH clauses that contain INSERT ... RETRUNING to return the generated keys. Then these “views for a single query” can be used to insert those keys into the referencing tables.

WITH par_key AS
        (INSERT INTO participante (nome) VALUES ('Laurenz') RETURNING id),
     ven_key AS
        (INSERT INTO venda (inicio) VALUES (current_date) RETURNING id),
     item_key AS
        (INSERT INTO item (nome) VALUES ('thing') RETURNING id)
INSERT INTO lances_vendas (venda_id, item_id, participante_id, valor)
   SELECT ven_key.id, item_key.id, par_key.id, numeric '3.1415'
   FROM par_key, ven_key, item_key;

Upvotes: 24

yglodt
yglodt

Reputation: 14551

You could create a function to do that job. Take a look at this example:

CREATE OR REPLACE FUNCTION import_test(p_title character varying, p_last_name character varying, p_first_name character varying, p_house_num integer, p_street character varying, p_zip_code character varying, p_city character varying, p_country character varying)
RETURNS integer
LANGUAGE plpgsql
AS
$body$
DECLARE

    address_id uuid;
    parent_id uuid;
    ts timestamp;

BEGIN

    address_id := uuid_generate_v4();
    parent_id := uuid_generate_v4();
    ts := current_timestamp;

    insert into address (id, number, street, zip_code, city, country, date_created) values (address_id, p_house_num, p_street, p_zip_code, p_city, p_country, ts);
    insert into person (id, title, last_name, first_name, home_address, date_created) values (parent_id, p_title, p_last_name, p_first_name, address_id, ts);

RETURN 0;
END;
$body$
VOLATILE
COST 100;

COMMIT;

Note how the generated UUID for the address (first insert) is used in the person-record (second insert)

Usage:

SELECT import_test('MR', 'MUSTERMANN', 'Peter', '[email protected]', 54, 'rue du Soleil', '1234', 'Arlon', 'be');
SELECT import_test('MS', 'MUSTERMANN', 'Peter 2', '[email protected]', 55, 'rue de la Lune', '56789', 'Amnéville', 'fr');

Upvotes: 2

Fabian Pijcke
Fabian Pijcke

Reputation: 3210

I know that you requested a single query, but you may still want to consider using a transaction:

BEGIN;
INSERT INTO participante (nome) VALUES ('Laurenz');
INSERT INTO venda (inicio) VALUES (current_date);
INSERT INTO item (nome) VALUES ('thing');
INSERT INTO lances_vendas (venda_id, item_id, participante_id, valer)
VALUES (currval('venda_id_seq'), currval('item_id_seq'), currval('participante_id_seq'), 3.1415);
COMMIT;

The transaction ensures that any new row in participante, venda and item leave the value of currval('X') unchanged.

Upvotes: 2

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