PostgreSQL: Sub-select inside insert

Use the INSERT INTO SELECT variant, including whatever constants right into the SELECT statement.

The PostgreSQL INSERT syntax is:

INSERT INTO table [ ( column [, ...] ) ]
 { DEFAULT VALUES | VALUES ( { expression | DEFAULT } [, ...] ) [, ...] | query }
 [ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ]

Take note of the query option at the end of the second line above.

Here is an example for you.

INSERT INTO 
    widgets
    (
        map_id,
        widget_name
    )
SELECT 
   mt.map_id,
   'Bupo'
FROM
    map_tags mt
WHERE
    mt.map_license="12345"