Multiple INSERTS into one table and many to many table

You can do it all in one SQL command using CTEs.

Assuming Postgres 9.6 and this classic many-to-many schema (since you did not provide it):

CREATE TABLE questions (  question_id serial PRIMARY KEY, title text NOT NULL, body text, userid int, categoryid int);CREATE TABLE tags (  tag_id serial PRIMARY KEY, tag text NOT NULL UNIQUE);CREATE TABLE questiontags (  question_id int REFERENCES questions, tag_id      int REFERENCES tags, PRIMARY KEY(question_id, tag_id));

To insert a single question with an array of tags:

WITH input_data(body, userid, title, categoryid, tags) AS (   VALUES (:title, :body, :userid, :tags)   ) , input_tags AS (                         -- fold duplicates      SELECT DISTINCT tag      FROM   input_data, unnest(tags::text[]) tag      ) , q AS (                                  -- insert question   INSERT INTO questions         (body, userid, title, categoryid)   SELECT body, userid, title, categoryid   FROM   input_data   RETURNING question_id   ) , t AS (                                  -- insert tags   INSERT INTO tags (tag)   TABLE  input_tags  -- short for: SELECT * FROM input_tags   ON     CONFLICT (tag) DO NOTHING        -- only new tags   RETURNING tag_id   )INSERT INTO questiontags (question_id, tag_id)SELECT q.question_id, t.tag_idFROM   q, (   SELECT tag_id   FROM   t                                -- newly inserted   UNION  ALL   SELECT tag_id   FROM   input_tags JOIN tags USING (tag) -- pre-existing   ) t;

dbfiddle here

This creates any tags that do not exist yet on the fly.

The text representation of a Postgres array looks like this: {tag1, tag2, tag3}.

If the input array is guaranteed to have distinct tags, you can remove DISTINCT from the CTE input_tags.

Detailed explanation:

• Insert data in 3 tables at a time using Postgres
• How to use RETURNING with ON CONFLICT in PostgreSQL?
• How to implement a many-to-many relationship in PostgreSQL?
• Cannot INSERT: ERROR: array value must start with "{" or dimension information

If you have concurrent writes you may have to do more. Consider the second link in particular.