How correctly create multiple entries by arrays in PostgreSQL? - sql

Question

In PostgreSQL database I have table which looks like this:
| question_id | question_text | widget | required | position |
|-------------|---------------|--------|----------|----------|
| int | text | int | boolean | int |
Second table which called factors_questions_relationship looks like this:
| factor_id | question_id |
|-------------|---------------|
| int | text |
I am trying to create function which would create multiple rows and return array of ids of new created entries. How correctly to make such function?
CREATE OR REPLACE FUNCTION factorio(
FACTOR_IDENTIFIER INT,
TEXT_ARR VARCHAR[],
WIDGET_ARR INT[],
REQUIRED_ARR BOOLEAN[],
POSITION_ARR INT[]
) RETURNS SETOF INT AS $$
BEGIN
RETURN QUERY
WITH RESULT_SET AS (
INSERT INTO QUESTIONS (TEXT, WIDGET, REQUIRED, POSITION)
SELECT
UNNEST(ARRAY[TEXT_ARR]) AS TEXT,
UNNEST(ARRAY[WIDGET_ARR]) AS WIDGET,
UNNEST(ARRAY[REQUIRED_ARR]) AS REQUIRED,
UNNEST(ARRAY[POSITION_ARR]) AS POSITION
RETURNING ID
)
--
INSERT INTO factors_questions_relationship (FACTOR_ID, QUESTION_ID)
SELECT FACTOR_IDENTIFIER FACTOR_ID, QUESTION_ID FROM UNNEST(ARRAY[array_agg(SELECT ID FROM RESULT_SET)]) QUESTION_ID
--
SELECT ID FROM RESULT_SET;
END;
$$ LANGUAGE plpgsql;

Answer 1

You can simply unnest them in columns
select
unnest(array['quick','brown','fox']) as question_text,
unnest(array[1,2,3]) as widget_id
Whereas putting them in FROM clause, would result to cartesian product:
select question_text, widget_id
from
unnest(array['quick','brown','fox']) as question_text,
unnest(array[1,2,3]) as widget_id
Output:
To obtain the Ids generated from newly-inserted records, use return query + returning id combo. Sample test:
create table z
(
id int generated by default as identity primary key,
question_text text
);
create or replace function insert_multiple_test()
returns table (someid int) as
$$
begin
return query
with resulting_rows as
(
insert into z(question_text) values
('hello'),
('你好'),
('hola')
returning id
)
select id from resulting_rows;
end;
$$ language 'plpgsql';
select * from insert_multiple_test();
Output:
Here's for SETOF:
create table z(id int generated by default as identity primary key, question_text text);
create or replace function insert_multiple_test()
returns setof int
as
$$
begin
return query
with resulting_rows as
(
insert into z(question_text) values
('hello'),
('你好'),
('hola')
returning id
)
select id from resulting_rows;
end;
$$ language 'plpgsql';
select x.the_id from insert_multiple_test() as x(the_id);
Output:
If you don't need to run multiple queries, you can just use LANGUAGE 'sql', it's simpler:
create table z
(
id int generated by default as identity primary key,
question_text text
);
create or replace function insert_multiple_test()
returns setof int as
$$
insert into z(question_text) values
('hello'),
('你好'),
('hola')
returning id;
$$ language 'sql';
select x.id_here from insert_multiple_test() as x(id_here);
Output: