Insert data in 3 tables at a time using Postgres

Use data-modifying CTEs:

WITH ins1 AS (   INSERT INTO sample(firstname, lastname)   VALUES ('fai55', 'shaggk')-- ON     CONFLICT DO NOTHING         -- optional addition in Postgres 9.5+   RETURNING id AS sample_id   ), ins2 AS (   INSERT INTO sample1 (sample_id, adddetails)   SELECT sample_id, 'ss' FROM ins1   RETURNING user_id   )INSERT INTO sample2 (user_id, value)SELECT user_id, 'ss2' FROM ins2;

Each INSERT depends on the one before. SELECT instead of VALUES makes sure nothing is inserted in subsidiary tables if no row is returned from a previous INSERT. (Since Postgres 9.5+ you might add an ON CONFLICT.)
It's also a bit shorter and faster this way.

Typically, it's more convenient to provide complete data rows in one place:

WITH data(firstname, lastname, adddetails, value) AS (   VALUES                              -- provide data here      ('fai55', 'shaggk', 'ss', 'ss2') -- see below    , ('fai56', 'XXaggk', 'xx', 'xx2') -- works for multiple input rows       --  more?                         ), ins1 AS (   INSERT INTO sample (firstname, lastname)   SELECT firstname, lastname          -- DISTINCT? see below   FROM   data   -- ON     CONFLICT DO NOTHING       -- UNIQUE constraint? see below   RETURNING firstname, lastname, id AS sample_id   ), ins2 AS (   INSERT INTO sample1 (sample_id, adddetails)   SELECT ins1.sample_id, d.adddetails   FROM   data d   JOIN   ins1 USING (firstname, lastname)   RETURNING sample_id, user_id   )INSERT INTO sample2 (user_id, value)SELECT ins2.user_id, d.valueFROM   data dJOIN   ins1 USING (firstname, lastname)JOIN   ins2 USING (sample_id);

db<>fiddle here

You may need explicit type casts in a stand-alone VALUES expression - as opposed to a VALUES expression attached to an INSERT where data types are derived from the target table. See:

• Casting NULL type when updating multiple rows

If multiple rows can come with identical (firstname, lastname), you may need to fold duplicates for the first INSERT:

...INSERT INTO sample (firstname, lastname)SELECT DISTINCT firstname, lastname FROM data...

You could use a (temporary) table as data source instead of the CTE data.

It would probably make sense to combine this with a UNIQUE constraint on (firstname, lastname) in the table and an ON CONFLICT clause in the query.

Related:

• How to use RETURNING with ON CONFLICT in PostgreSQL?
• Is SELECT or INSERT in a function prone to race conditions?

Something like this

with first_insert as (   insert into sample(firstname,lastname)    values('fai55','shaggk')    RETURNING id), second_insert as (  insert into sample1( id ,adddetails)   values  ( (select id from first_insert), 'ss')  RETURNING user_id)insert into sample2 ( id ,adddetails) values ( (select user_id from first_insert), 'ss');

As the generated id from the insert into sample2 is not needed, I removed the returning clause from the last insert.

Typically, you'd use a transaction to avoid writing complicated queries.

http://www.postgresql.org/docs/current/static/sql-begin.html

http://dev.mysql.com/doc/refman/5.7/en/commit.html

You could also use a CTE, assuming your Postgres tag is correct. For instance:

with sample_ids as (  insert into sample(firstname, lastname)  values('fai55','shaggk')  RETURNING id), sample1_ids as (  insert into sample1(id, adddetails)  select id,'ss'  from sample_ids  RETURNING id, user_id)insert into sample2(id, user_id, value)select id, user_id, 'val'from sample1_idsRETURNING id, user_id;