PostgreSQL insert array many-to-many relationship

Question

Let many users belong to many groups.

Write a function that creates a group with a name and a list of users.

Answer 1

CREATE FUNCTION groups_create(varchar(50), bigint[]) RETURNS SETOF bigint AS
$$
    WITH g AS (
        INSERT INTO groups (name)
        VALUES ($1)
        RETURNING id
    ), gm AS (
        INSERT INTO group_members
        SELECT id, unnest($2) FROM g
    )
    SELECT id FROM g
$$
LANGUAGE SQL;

http://sqlfiddle.com/#!15/9e408/9