Create a table based on few columns of another table, but also add some additional columns

Question

I know I can do something like this:

CREATE TABLE new_table AS (
    SELECT field1, field2, field3
    FROM my_table
)

I'm wondering how do I add more columns to this create table SQL, that are not from my_table, but instead ones that I would write my self and which would be unique to this new_table only.

I know I could just make the table with the above SQL and then additionaly (after the command is completed) add the necessary columns, but am wondering if this all could be done in one command, maybe something like this (tried it like that, but didn't work):

CREATE TABLE new_table AS (
    (SELECT field1, field2, field3
    FROM my_table),
    additional_field1 INTEGER NOT NULL DEFAULT 1,
    additional_field2 VARCHAR(20) NOT NULL DEFAULT 1
)

Answer 1

You can also explicitly specify the data type for a generated column:

See Create Table Select Manual

CREATE TABLE new_table
(
 additional_field1 INTEGER NOT NULL DEFAULT 1,
 additional_field2 VARCHAR(20) NOT NULL DEFAULT 1
)
AS
(
 SELECT id, val,
        1 AS additional_field1,
        1 AS additional_field2
 FROM my_table
);

Example: SQLFiddle